Clinicians › Shoulder

Shoulder Instability

Traumatic unidirectional and atraumatic multidirectional instability — pathomechanics, structural failure patterns, and clinical differentiation for treatment planning.

218 citationsUpdated Sep 2026

For patients: a plain-language version of this topic is available. See the patient guide.

Overview

Shoulder instability encompasses anterior, posterior, and multidirectional (MDI) patterns, with posterior glenohumeral instability accounting for 2% to 5% of all cases [14]. MDI is defined by inferior laxity alongside anterior and/or posterior laxity [4]. Clinical presentation varies; traumatic posterior dislocations are frequently undiagnosed in emergency settings, with up to 50% missed upon initial presentation [14]. The MOON Shoulder Instability Study represents the largest cohort of patients undergoing stabilization to date [2]. A review evaluates sex-based differences in occurrence, treatment, and functional outcomes [18]. Proper evaluation of bone loss is critical for determining surgical indications and outcomes [10].

Indications for operative intervention include persistent pain and instability interfering with normal or sport-related activity after failure of extensive nonsurgical management [4, 14]. Nonsurgical treatment is always attempted first for posterior instability [14] and involves 6 to 9 months of physical therapy focusing on rotator cuff strengthening, scapular kinematics, and proprioception for MDI [4]. Surgery is contraindicated for voluntary dislocators and patients who have not attempted physical therapy [4, 14]. Preoperative assessment must identify all directions of instability and anatomic factors such as humeral head or glenoid defects, rotator cuff tears, or generalized ligamentous laxity [16].

Headline outcomes indicate that arthroscopic posterior capsulolabral repair is durable, with 90% of athletes returning to sport at 3 years [16] and 92% stability at 5 years in adolescents [16]. Long-term follow-up of 15.4 years confirms improved pain and function [229]. Recurrence is the most common complication, reported at 8.5% in the general population and higher in overhead athletes [14]. Recurrence rates increase with posterior glenoid bone loss greater than 20%, which contraindicates arthroscopic soft-tissue stabilization alone [14]. The Western Ontario Shoulder Instability Index (WOSI) is recommended for follow-up [30], and consensus statements aim to standardize outcome measurement and tailored treatment based on pathology and patient demands [20].

Anatomy & Pathophysiology

Bony Anatomy

The glenohumeral joint relies heavily on soft tissue stabilizers because the bony anatomy contributes little to inherent stability, often compared to a golf ball on a tee [100]. The glenoid cavity is a shallow, convex socket shaped like an inverted pear, approximately one-third the size of the humeral head [88, 100]. The subchondral bone is relatively flat, with the articular concavity augmented by cartilage and a circumferential labrum to create a socket approximately 9 mm deep superoinferiorly and 5 mm deep anteroposteriorly [92, 100]. The glenoid averages 5° of retroversion relative to the scapular body axis [92]. The humeral head is essentially spherical with a radius of curvature of approximately 25 mm, while the glenoid articular surface radius is 2 to 3 mm larger [99]. The superior margin of the humeral head articular surface lies 8 to 10 mm superior to the top of the greater tuberosity [99]. The distance from the lateral base of the coracoid process to the lateral margin of the greater tuberosity defines the lateral humeral offset [99].

Humeral head orientation averages 19° of retroversion and 41° of inclination, with a neck-shaft angle averaging 135 degrees [90, 92]. Alternatively, the humeral head is retroverted an average of 30 degrees relative to the transepicondylar axis of the humerus [102]. The scapula is anteverted on the chest wall approximately 30 degrees relative to the body [102]. In the developing shoulder, the proximal humerus has three ossification centers: the humeral head (4 to 6 months), the greater tuberosity (1 to 3 years), and the lesser tuberosity (3 to 5 years) [92]. Humeral retroversion averages 65 degrees in infants and young children, gradually decreasing to adult values by 11 years of age [96]. The proximal humeral physis closes by 14 to 17 years in girls and 16 to 18 years in boys [96]. Biomechanical studies indicate that the coracoid process has increased in size over time; with the shoulder in 90 degrees of abduction, the coracoid extension over the glenohumeral joint mechanically limits anterior translation of the humerus relative to the glenoid [97].

Soft Tissue Anatomy & Stabilizers

Static stabilizers of the glenohumeral joint include articular congruity, the glenoid labrum, concavity-compression, negative intra-articular pressure, and the glenohumeral capsule and ligaments [92]. The fibrocartilaginous glenoid labrum deepens the socket by 50% and provides a bumper to translation [92, 102]. Dynamic stabilizers include the rotator cuff and biceps tendon, with scapulothoracic mechanics also contributing to stability [102]. The rotator interval is defined medially by the base of the coracoid, superiorly by the supraspinatus tendon, and inferiorly by the subscapularis tendon [92]. This interval contains the coracohumeral ligament, the superior glenohumeral ligament, and the intra-articular portion of the long head of the biceps tendon [92]. Laxity of the rotator interval results in inferior laxity (the sulcus sign), while contracture is seen with adhesive capsulitis [92].

The coracohumeral ligament originates from the base and lateral border of the coracoid process just below the origin of the coracoacromial ligament and inserts on the greater tuberosity [106]. It restricts external rotation in adduction and acts as a static restraint to inferior and posterior translation in adduction and external rotation [92]. The superior glenohumeral ligament is a primary static restraint against anterior translation with the arm at the side [92]. The middle glenohumeral ligament is a primary static restraint against anterior translation with the arm in external rotation and 45° of abduction, though it is absent in up to 30% of shoulders [92, 102]. The anterior band of the inferior glenohumeral ligament is a primary static restraint against anterior-inferior dislocation in 90° of abduction and external rotation [92]. The posterior band of the inferior glenohumeral ligament is a primary static restraint against posterior-inferior translation in internal rotation and adduction [92].

The shoulder capsule is large, having twice the surface area of the humeral head and typically accepting approximately 28 to 35 mL of fluid [106]. In adhesive capsulitis, the capsule accepts only 5 mL or less, whereas in considerable laxity or instability it accepts larger volumes [106]. The transverse humeral ligament consists of transverse fibers of capsule extending between the greater and lesser tuberosities to contain the long head of the biceps tendon in its groove [106]. Rotator cuff muscle tendons blend into the capsule over varying lengths averaging approximately 2.5 cm [106]. The subscapularis is the largest and strongest rotator cuff tendon, responsible for active internal rotation and contributing to shoulder stability [202]. It forms the anterior portion of the transverse plane "force couple" of the rotator cuff to balance forces across the joint and maintain glenohumeral congruency [202]. Evolutionary changes have broadened the infraspinatus fossa, making the infraspinatus and teres minor more effective as depressors and external rotators of the humeral head [97]. The acromion has also enlarged over evolutionary time, reflecting the increasing role of the deltoid muscle in shoulder function [97].

Pathophysiology & Mechanisms

The glenohumeral joint depends on static and dynamic stabilizers for movement and stability because the bony anatomy contributes little to stability [100]. The limited joint volume effect provides stability through negative intra-articular pressure, which is reduced if the joint is vented or if capsular boundaries are very compliant [304]. Venting the capsule with an 18-gauge needle reduced the force necessary to translate the humeral head halfway to the edge of the glenoid by an average of 50% [304]. Unstable shoulder joints with a Bankart lesion do not exhibit the phenomenon of negative intra-articular pressure generated by traction on the arm [304]. In patients with loose shoulders, collagen fibers in the capsule, muscles, and skin are relatively immature, more soluble, and less cross-linked than those in controls [304]. A positive family history of shoulder instability was found in 24% of patients who required surgery for anterior glenohumeral instability [304]. A positive family history was noted twice as often in patients whose postoperative course was complicated by recurrent instability [304].

Traumatic anterior instability usually affects shoulders that are not lax, enabling the applied force to avulse the labrum from the anteroinferior glenoid [27]. Lax shoulders may be dislocatable but typically do not have labral avulsions, requiring management that may include labral augmentation and capsular tightening [27]. In AMBRI-type instability, the capsule is likely to be more stretchy than usual and the labrum more compressible, allowing humeral head translation due to failure of the concavity compression mechanism [27]. An anteroinferior Bankart labral detachment is present in the majority of recurrently unstable shoulders after an initial traumatic dislocation [28]. Most shoulders with recurrent instability have a certain degree of coexisting capsular redundancy at the time of surgery [28]. As acute dislocation evolves into chronic, recurrent instability, further capsular attenuation is likely to occur [28]. Isolated labral reattachment is usually inadequate and results in failure in patients with more than two or three instability episodes and/or significant capsular attenuation [28].

Capsular laxity is the essential lesion in multidirectional instability [52]. Increased capsular volume and cross-sectional area are nonspecific findings common to many patients with capsular laxity and recurrent instability [52]. Injury to the rotator interval is an important component of anterior capsular injury in general [52]. Shallow glenoid morphology has been identified as a contributing factor in some cases of multidirectional instability [52]. Voluntary dislocators with a component of natural laxity and untreated skeletal dyskinesia can become involuntary dislocators with labral tears or capsular pathology [52]. Multidirectional instability is characterized by generalized ligamentous laxity, as well as abnormal shoulder and scapular kinematics [52]. The contralateral shoulder in patients with multidirectional instability may exhibit many of the same characteristics but may or may not be symptomatic [52].

Posterior glenohumeral instability is less common, accounting for 2% to 5% of all glenohumeral instability [14]. Posterior instability occurs with high frequency in association with combined traumatic anterior instability, with 40% of operative instability cases containing posterior instability combined with anterior instability identified at the time of surgery [16]. MRI is inadequate for detecting combined posterior and anterior instability pathology [16]. The posterior band of the inferior glenohumeral ligament is thinner than the anterior band, which may predispose these tissues to specific changes in response to certain mechanisms of injury [275]. The posterior capsule has a tendency to plastically deform in response to repetitive, posteriorly directed forces [275]. In overhead athletes, adaptive changes such as glenohumeral internal rotation deficit (GIRD) are consequences of anatomic factors including humeral retrotorsion, contractures of the coracohumeral ligament, pectoralis, and anterior deltoid, and dynamic muscle stiffness [275]. The phenomenon of thixotropy may explain the acute changes in glenohumeral range of motion noted after an acute throwing episode [275].

Repetitive microtrauma in the throwing shoulder causes attrition and gradual failure, with typical sites of pathoanatomy including the superior and posterosuperior labrum, the articular surface of the supraspinatus and infraspinatus, and the posterior capsule [129]. Injury to the thrower’s shoulder joint occurs most commonly in the late cocking or early acceleration phases [129]. A combination of abnormal scapulothoracic and glenohumeral motion can injure the superior and posterosuperior labrum as well as the undersurface of the rotator cuff and posterior capsule [129]. Internal impingement occurs in 90 degrees of abduction and 90 degrees of external rotation where the posterosuperior rotator cuff contacts the posterosuperior glenoid labrum [220]. Excessive contact of the undersurface of the rotator cuff and the superior labrum during repetitive overhead activity can lead to articular-sided rotator cuff tears and SLAP lesions in throwers [220]. Labral tears were present in 100% of 36 competitive athletes with articular-sided, partial-thickness rotator cuff tears, of whom 64% were baseball pitchers [220]. Superior labral fraying was found in 90% of patients with partial-thickness rotator cuff tears [220]. The "peel-back" mechanism involves the biceps tendon transmitting a torsional force to the posterior labrum during external rotation and abduction, potentially peeling it back [220]. Glenohumeral internal rotation deficit (GIRD) allows supraphysiologic external rotation with fatigue failure of the rotator cuff fibers, potentially leading to a pathologic state [220]. Posterior capsular contracture initiates a cascade where posterosuperior instability shifts the humeral head posterosuperiorly, affecting kinetic chain dynamics and leading to loss of internal rotation and arm acceleration [220]. Attenuation of the anterior capsule can occur with continued throwing, leading to eventual permanent deformation and anterior microinstability [220].

A secondary subacromial impingement related to occult shoulder instability is a pathology that usually involves young active people [42]. In patients with underlying glenohumeral instability, shoulder pain and subacromial impingement symptoms are probably due to rotator cuff dysfunction or secondary subacromial bursitis with pain and secondary inhibition of cuff function [42]. Rotator cuff fatigue from eccentric contraction allows the humeral head to translate anteriorly and superiorly, causing secondary impingement [42]. Multiple anterior shoulder dislocations lead to abnormal translational kinematics and result in increased superior translation of the humerus [196]. Simulated anterosuperior rotator cuff tears involving the superior half of the subscapularis significantly alter shoulder biomechanics and lead to increased anterosuperior and superior glenohumeral translation under higher loads [154]. Tears of the subscapularis have greater biomechanical consequences than do tears of the infraspinatus [150]. Partial-thickness articular-sided rotator cuff tears with a thickness >50% involving the rotator cable increased glenohumeral translation and changed kinematics in a cadaveric biomechanical model [176]. Biomechanical changes of passive glenohumeral joint motion occur in the glenohumeral joint with as little as 5% glenohumeral internal rotation deficit [149]. During the simulated acceleration phase of the throwing motion, anterior glenohumeral translation significantly increased as shoulder abduction decreased [182].

The Latarjet procedure leads to anatomic and biomechanical changes in the shoulder [104]. The modified position of the scapula after a Latarjet procedure is maintained during the entire range of motion, suggesting a shoulder-stabilizing kinematic effect in addition to bony, sling, and bumper effects [180]. Both the coracobrachialis and short head of biceps had increased extension and internal rotation moment arms at higher degrees of elevation compared with native shoulders following a Latarjet procedure [195]. Capsular repair significantly alters normal glenohumeral kinematics [147]. In the setting of shoulder instability without evidence of a labral tear, the capsulolabral advancement technique may be considered biomechanically superior to suture capsulorrhaphy [165]. Time-zero biomechanical shoulder instability studies are valuable but limited because they do not replicate clinical dynamics [183]. Biomechanical studies on posterior shoulder instability remain limited in the literature, with current models performed in a static manner which limits their translation for explaining a dynamic pathology [21]. The biomechanical shoulder model is consistent with clinical observations regarding the effects of glenoid inclination and acromion index on humeral head translation and glenoid articular cartilage strain [89]. Glenohumeral decentering is significantly associated with diminished shoulder function and active range of motion in all planes [172]. Arm kinematic analyses suggest that open surgery stabilizes the shoulder but does not necessarily restore normal movement quality [175]. Kinematic analysis of patients with rotator cuff tears shows unexpected inferior, rather than superior, translation of the humeral head [189]. Antero-inferior glenohumeral instability is associated with an abnormal position of the coracoid process [190]. Pelvic position affects shoulder range of motion [194]. Clavicle shortening of >10% greatly affects scapular kinematics in vivo [163]. Shortening of the clavicle affects the kinematics in the shoulder girdle [116]. Scapular and clavicular kinematics were affected in acromioclavicular separation models [197]. The trapezoid and conoid ligaments have unique functions in normal shoulder kinematics because of their anatomic attachments [178]. Although each reconstruction technique for coracoclavicular, acromioclavicular, or combined injuries was able to restore different elements of joint kinematics, none of the strategies completely restored the shoulder girdle to its pre

Classification

Rockwood: In 1979, Rockwood distinguished shoulder instabilities based on the presence or absence of trauma [1].

Thomas and Matsen: This classification introduced the AMBRI acronym for atraumatic multidirectional instability, which is often bilateral and requires rehabilitation and inferior capsular shift [1]. It also introduced the TUBS acronym for traumatic unidirectional instability, which involves a Bankart lesion and often requires surgery [1].

Stanmore: Introduced in 2004, this classification encompasses Polar type I (true TUBS), Polar type II (true AMBRI), and Polar type III (atraumatic with functional origin due to muscle patterning disorders or habitual non-structural instability) [1]. It also encompasses presentations of instability that combine multiple categories [1].

Gerber et al.: This classification includes chronic locked dislocation, unidirectional instability without hyperlaxity, unidirectional instability with hyperlaxity, multidirectional instability without hyperlaxity, multidirectional instability with multidirectional hyperlaxity, and uni- or multidirectional voluntary instability [53].

ABC: This classification distinguishes three groups of posterior glenohumeral instability based on the nature of pathology (first-time, dynamic, or static) [58]. It includes two different subtypes for each of the three groups based on pathomechanical causes [58]. The ABC classification aims to facilitate diagnosis and assist the treatment decision-making process for posterior shoulder instability [58]. An international expert Delphi consensus statement recommends classifying posterior shoulder instability by the ABC classification [77]. The system distinguishes three groups with two subtypes based on the pathomechanical type of instability and the current standard of treatment [170].

FEDS: This system categorizes instability based on frequency, aetiology, direction, and severity [113]. The FEDS classification, particularly the frequency and etiology of the patient's shoulder instability, may be helpful in identifying patients with a higher likelihood of undergoing surgical treatment [46]. The FEDS system has content validity and is highly reliable for classifying glenohumeral instability [210].

Walch: In the glenoid hull study, 109 shoulders with primary glenohumeral osteoarthritis were classified according to the Walch classification [293]. The distribution included 36 shoulders (33%) as Walch type A1, 21 shoulders (19%) as Walch type A2, 20 shoulders (18%) as Walch type B1, 28 shoulders (26.5%) as Walch type B2, and 4 shoulders (3.5%) as Walch type C2 [293].

Baker et al.: This classification defines intra-articular pathology in three groups [295]. Group 1 includes shoulders with a capsular tear and no Bankart lesion [295]. Group 2 includes shoulders that are unstable with a partial labral separation [295]. Group 3 includes shoulders that are unstable with a complete labral detachment [295].

Snyder: For experienced shoulder surgeons, the Snyder classification is a reliable system for identifying SLAP lesions [209].

Other Considerations: Non-traumatic shoulder instability (NTSI) is defined as abnormal movement or position of the shoulder leading to pain, subluxation, dislocation, or functional discomfort without a significant history of injury [1]. Since the 1980s, 18 classifications have been developed to define sub-groups of shoulder instability, but none have demonstrated strong measurement properties [1]. The authors of a 2004 Current Orthopaedics paper propose a classification system that is all-inclusive and recognizes that more than one pathology can occur in an individual shoulder [5]. This proposed system challenges previous systems by being all inclusive and recognising that more than one pathology can occur in an individual shoulder [5]. A systematic review highlights the need for a consensus on the definition of recurrence across shoulder instability studies [9]. The 2009 Consensus Statement on Shoulder Instability aims to improve diagnosis and treatment through universal agreement on outcome measurement tools and tailored treatment based on pathology, patient age, activity demands, and surgeon skills [20]. The Delphi method was used to generate an international consensus statement on shoulder instability covering diagnosis, nonoperative management, surgical options, rehabilitation, and clinical follow-up [23]. There are discrepancies in the definition and classification of multidirectional instability, which can make diagnosis and treatment selection challenging [193]. Hyperlaxity is characterized as an individual constitution rather than a primary disease, and multidirectional instability should be distinguished from multidirectional hyperlaxity in the classification of shoulder instability [53].

Static instabilities are defined by the absence of classic symptoms of instability yet the humeral head is displaced and fixed superior, anterior, or posterior relative to its normal position on the glenoid fossa [53]. The diagnosis of static instability is radiological, not clinical, and it may remain asymptomatic for a long period [53]. Static instabilities can co-exist with dynamic instabilities; usually, the more disabling instability is dynamic and is best treated initially when static and dynamic instabilities co-exist [53]. Static superior migration of the humeral head is present if the normal distance between the undersurface of the acromion and the most cranial aspect of the humeral head on an AP radiograph with the shoulder in neutral rotation is decreased, with seven millimetres currently used to define static superior subluxation [53]. The cause of cranial migration seems to be insufficiency of the infraspinatus in the presence of a supraspinatus tear, whereas isolated supraspinatus, isolated infraspinatus, or combination tears of the supraspinatus and subscapularis tendons do not cause static superior instability [53]. Loss of the acromio humeral distance to less than 7 mm is associated with loss of strength of abduction and of external rotation [53]. Static superior subluxation carries a poor prognosis for repair of the rotator cuff tear, and some consider it a predictor of an irreparable tear; in the current authors’ experience, superior static subluxation is essentially irreversible by conventional repair techniques [53].

Static anterior subluxation is a fixed anterior position of the humeral head on the glenoid fossa, often manifest clinically as moderate to severe shoulder pain caused by impingement under the coracoid and coracoacromial arch and loss of anterior elevation [53]. It is usually detected on CT or MRI scans taken with the arm in neutral rotation but occasionally may be evident on axillary lateral radiographs [53]. Static anterior subluxation usually is not associated with recurrent anterior shoulder instability [53]. To develop a static anterior subluxation without any previous operation, a combination of a subscapularis tear, a supraspinatus tear, and fatty degeneration of the infraspinatus muscle seems necessary, while an isolated tear of the subscapularis tendon and posterosuperior tears usually do not lead to anterior static subluxation [53]. In the current authors’ experience to date (2002), static anterior subluxation has been irreversible with soft tissue procedure [53].

Static posterior subluxation is a fixed posterior position of the humeral head on the glenoid fossa on CT or MRI scans with the arm in neutral rotation [53]. It is most frequently but not always associated with congenital dysplasia of the glenoid or with degenerative glenohumeral joint disease, and may be associated with glenoid deformations such as classified by Walch and co-workers [53]. Static posterior subluxation may be present without any rotator cuff deficiencies, and most authors have found static posterior subluxations to be irreversible [53].

Inferior subluxation of the shoulder is characterized by straight inferior translation of the humerus relative to the glenoid fossa [53]. It may occur from trauma, neurologic injury, septic arthritis, or inadequate restoration of humeral length after arthroplasty [53]. Inferior subluxation after trauma and surgery, if not associated with permanent nerve injury, usually resolves within 6 weeks but always resolves within 2 years [53]. Inferior subluxation caused by infection tends to result in joint surface destruction and only successful treatment of infection results in resolution of the inferior subluxation [53]. Inferior subluxation caused by neurologic injury or shortening of the humerus remains symptomatic unless the primary problem can be resolved [53].

Failure of primary shoulder stabilization procedures is often related to uncorrected anatomic pathology, and the instability severity index score permits precise identification of patients at risk for failure of primary shoulder stabilization procedures [22]. Substantial variability was observed in the scoring of important elements in the radiological report for the evaluation of anterior shoulder instability regardless of modality [25]. Shoulder anatomy is particularly complex and requires thorough knowledge by the orthopedic surgeon, and anatomical variants should not be confounded with pathological findings when treating shoulder instability [32]. Different anatomical lesions can be found depending on the type of instability and the functional requirements of the patient [32]. An expanded assessment framework is useful to estimate the contribution of each component of non-traumatic shoulder instability and offer a framework for targeted rehabilitation, although the validity of testing specific subgroups within this framework remains to be established [43]. The paper by Jaggi and Lambert reviews the nonoperative treatment and postoperative management of patients with various classifications of shoulder instability [51].

The MOON Shoulder Group is made up of 16 fellowship-trained orthopaedic surgeons and research personnel from nine academic and private practice sites in the United States, initially formed to identify research questions related to treatment of rotator cuff disease but has expanded its scope to include other shoulder pathology [3]. MOON Shoulder Instability is an offshoot of MOON Shoulder, focusing on patients undergoing surgical treatment for shoulder instability, with early studies describing baseline demographics, modifying factors, and limited early outcomes [3]. The review evaluates existing data on the presentation of shoulder instability in men and women to determine if there are differences in occurrence, treatment, or functional outcome following management [18]. Many different diagnostic examinations for assessing shoulder instability are used and a high variety is seen in the use of diagnostic tools [19]. The incidence of shoulder arthropathy in patients with shoulder instability is difficult to measure, and the high rate of recurrence seen with shoulder dislocation ranges from 10% to 90% after an initial dislocation [75]. There is no doubt that the humeral head suffers cartilage damage with shoulder dislocation [75]. Taylor and Arciero reported a series of 63 patients with first-time traumatic dislocations who were evaluated arthroscopically within 10 days of their dislocation, noting osteochondral lesions in 34 patients and chondral lesions in an additional 23 patients [75]. Norlin reported a series of 24 patients with first-time anterior shoulder dislocation assessed arthroscopically 1 to 3 days after injury, finding osteochondral lesions in six shoulders and chondral lesions in the remaining 18 shoulders [75]. Cameron et al reported on a series of 422 patients with a diagnosis of shoulder instability and no history of previous shoulder surgery who underwent an arthroscopic procedure, rating chondral damage according to the Outerbridge classification system [75]. Of the 88 patients with acute instability in the Cameron et al series, 24% had grade I or higher chondral lesions and 12% had Grade III or IV chondral damage [75].

The proposed classification system for glenoid bone loss is a helpful guide to the degree of glenoid bone loss when embarking on revision shoulder arthroplasty [208]. Objective and subjective scoring systems correlate significantly with the clinical condition of patients with recurrent shoulder instability and associated bony defects [212]. The formation of clusters based on glenoid morphology indicates that patterns exist in the types of glenoid defects, highlighting a need to further investigate a three-dimensional classification system and potentially new standardized revision implant component designs [217]. This study showed that there are different patterns of subcritical bipolar bone lesions in anterior shoulder instability, which can be divided into 4 groups with a significantly different prevalence [298]. Subcritical bipolar bone lesion patterns are significant predictors of failure after surgery, and surgeons should be aware that additional procedures may be considered depending on a specific pattern of subcritical bipolar bone lesion [298]. Shoulder instability cannot reliably be classified using the ICD-9 coding system [131].

Clinical Presentation

General Presentation and Definitions

Shoulder instability is defined as abnormal movement or position of the shoulder leading to pain, subluxation, or dislocation without a significant history of injury [1]. This condition is distinguished from asymptomatic laxity by the presence of symptoms [69]. In many cases, there is no history of a traumatic event, with genetic factors in ligamentous laxity recognized as significant in the perception of instability [69]. The classic patient with traumatic instability is a male athlete who sustained an identifiable traumatic event during violent activity [69]. Conversely, the classic patient with multidirectional shoulder instability is a young, asthenic female ballet dancer, swimmer, or volleyball player with nondescript shoulder pain involving the scapula and provoking paresthesia down the arm in the absence of a defined traumatic event [69].

Patients with atraumatic instability are typically younger than 30 years and experience discomfort and dysfunction in ordinary activities of daily living [236]. The onset is usually insidious but can occur after a minor injury or period of disuse [236]. Atraumatic instability typically causes the greatest difficulty with sleeping, lifting overhead, and throwing [236]. Pain is the more common symptom with shoulder instability based on ligamentous laxity (AMBRI), whereas apprehension is more common with unidirectional traumatic instability (TUBS) [69]. True symptomatic multidirectional instability is typically symptomatic in midrange positions before ligament tension reaches the end of its range [69]. Patients with multidirectional instability may exhibit symptoms so incapacitating that they tend to avoid extremes of glenohumeral motion [69]. The association of shoulder instability symptoms with paresthesia down the arm is nearly always related to shoulder instability [69]. A history of repetitive microtrauma from activities such as swimming, gymnastics, or ballet may be associated with subtle instability patterns [69].

Multidirectional instability has variable presentations and is difficult to quantify, characterized by inferior laxity in addition to anterior and/or posterior laxity [4]. Symptoms of multidirectional instability include pain, weakness, ipsilateral paresthesias, popping or clicking of the shoulder, instability during sleep, difficulty with throwing, and pain when carrying heavy objects [4]. Differential diagnoses for multidirectional instability include unidirectional shoulder instability, cervical disease, brachial plexitis, and thoracic outlet syndrome [4]. Rotator cuff tendinitis in an individual younger than 20 years should raise concern for multidirectional instability [4]. Patients with multidirectional instability may present with positive anterior and posterior apprehension, a pathologic sulcus sign with no history of trauma, and no history of dislocation requiring reduction [52].

Minor or occult shoulder instability can present with extra-articular subacromial impingement symptoms, primarily in young active people [42]. Secondary subacromial impingement related to occult shoulder instability is a pathology that usually involves people younger than 35 years of age most commonly involved in overhead athletic activities [42]. Microinstability is diagnostically challenging and can be diagnosed in young patients with ambiguous shoulder pain during motion, without instability [132]. Pain can serve as a clinical indicator of larger labral pathology in patients presenting with shoulder instability [111]. Patients do not always recognize anterior shoulder instability, and initial physical examination may be limited in the acute setting [110]. Traumatic shoulder instability in the older patient may result in a wide array of pathologic findings as well as a diversity of clinical presentations [105]. In children and adolescents with anterior shoulder instability, instability lesions vary significantly by age, with atypical lesions more common in patients younger than 15 years and bone loss associated with older age at presentation [143]. Children and adolescents with all forms of shoulder instability demonstrate differences in their movement and muscle activity patterns when compared to age- and sex-matched controls [36].

Anterior Instability Presentation

An acutely dislocated shoulder is usually very painful, with muscles in spasm in an attempt to stabilize the joint [162]. In anterior dislocation, the humeral head may be palpable anteriorly, and the posterior and lateral aspect of the shoulder shows a hollow beneath the acromion [162]. The arm in an anteriorly dislocated shoulder is held in slight abduction, and passive and active motions are limited by pain [162]. Injury with the arm in extension, abduction, and external rotation favors anterior dislocation [162]. A history of trauma with the arm locked in internal rotation is associated with posterior instability, while traumatic anterior instability often involves a history of a trip to the emergency department and radiographs documenting the events [69].

Traumatic instability can occur without a complete dislocation, manifesting as apprehension or subluxation when the arm is placed near the position of injury [236]. A shoulder with traumatic instability is comfortable when troublesome positions are avoided, but apprehension or fear of instability can prevent the patient from returning to work or sports [236]. Recurrent subluxation or dislocation in traumatic instability can occur when the shoulder is unexpectedly forced into the abducted, externally rotated position or during sleep [236]. Patients with traumatic instability may have a history of increasing ease of dislocation as remaining stabilizing factors are progressively compromised [236]. Seventy percent of patients younger than 22 years had recurrent instability, with 50% requiring surgical stabilization [31]. Young age, male sex, and hyperlaxity are clear risk factors for failure of conservative treatment in anterior shoulder instability [31].

Multiple episodes of instability have been linked to increased attritional glenoid bone loss, increased procedural complexity, increased severity of glenoid chondral defects, compromised outcomes at the time of surgical stabilization, and higher rates of glenohumeral osteoarthritis [31]. A large 2017 cohort study showed subjective instability in 62% and revision surgery in 32% of patients undergoing arthroscopic Bankart repair after multiple episodes of instability [31]. These rates of subjective instability and revision surgery were fourfold higher than in first-time dislocators [31]. Recurrent anterior instability of the shoulder is a complex disorder which mainly affects younger population, and generally requires surgical intervention to restore joint stability [140]. HAGL lesions are a rare and underdiagnosed cause of anterior shoulder instability that can lead to recurrent dislocations if unaddressed [135]. GAGL lesions are an uncommon cause of anterior shoulder instability and require a high level of suspicion [137].

Posterior Instability Presentation

The presentation of posterior instability is typically more subtle than anterior instability and is far less common, with an incidence rate of 4 per 1,000 person-years [68]. Recurrent posterior shoulder instability is an uncommon condition often unrecognized, leading to incorrect diagnoses and delays [33]. In most cases of posterior instability, no acute traumatic event occurs, and patients complain primarily of vague posterior shoulder pain [68]. Posterior shoulder dislocations are rarely associated with traumatic events that include falls [69]. Posterior shoulder instability is seen most often in the scenario of electric shocks and epilepsy [69]. Electoshock, seizures, or a fall on the flexed and adducted arm are commonly associated with posterior dislocation [162].

An acute posterior dislocation will present with a prominent posterior shoulder and anterior coracoid and a limited ability to externally rotate the shoulder [14]. The classic features of a posterior dislocation include limited external rotation of the shoulder, often to less than 0 degrees [162]. Limited elevation of the arm, often to less than 90 degrees, is a classic feature of posterior dislocation [162]. Posterior prominence and rounding of the shoulder in comparison to the normal side is a classic feature of posterior dislocation [162]. Flattening of the anterior aspect of the shoulder is a classic feature of posterior dislocation [162]. Prominence of the coracoid process on the dislocated side is a classic feature of posterior dislocation [162]. Asymmetry of the shoulder contours can often best be visualized by viewing the shoulders from above while standing behind the patient [162]. Motion is limited in posterior dislocation because the head of the humerus is fixed on the posterior glenoid rim by muscle forces or impaled on the glenoid rim [162].

Patients with old, unreduced posterior dislocations of the shoulder can have 30 to 40 degrees of glenohumeral abduction and some humeral rotation as a result of enlargement of the groove [162]. With long-standing disuse of the muscles about the shoulder in posterior dislocation, atrophy will be present, accentuating the flattening of the anterior portion of the shoulder, the prominence of the coracoid, and the fullness of the posterior portion [162]. In the interval before diagnosis, posterior dislocation may be misdiagnosed as a frozen shoulder for which vigorous therapy may be mistakenly instituted [162]. A unique presentation of posterior instability is the locked posterior dislocation, which most commonly occurs with violent trauma or a seizure [68]. Locked posterior dislocation should be recognized promptly based on a fixed shoulder deformity with loss of shoulder rotation [68]. Fixed posterior dislocations are often associated with a large reverse Hill-Sachs lesion that requires surgical intervention [68]. The PHAGL lesion is challenging to diagnose clinically and can be the cause of posterior instability or a component of the spectrum of shoulder instability [127].

Multidirectional Instability Presentation

Multidirectional instability is instability in all three directions: anterior, posterior, and inferior [52]. In some cases, multidirectional instability has been defined as dislocation in two directions, with subluxation in the remaining direction [52]. True multidirectional instability, in that the translations are symptomatic in all directions, is uncommon [52]. Multidirectional instability can have a traumatic or atraumatic etiology, or a combination [52]. Patients with instability in multiple directions can have voluntary or involuntary dislocations [52]. A traumatic component in multidirectional instability can exist from recurrent instability episodes and accrued microtrauma or from a traumatic injury in a patient with ligamentous laxity and preexisting evidence of multidirectional instability [52]. Shallow glenoid morphology has also been identified as a contributing factor in some cases of multidirectional instability [52]. There are two commonly associated anatomic lesions in multidirectional instability: a patulous inferior capsule which contains both the anterior and posterior bands of the IGHL and functional deficiency of the rotator interval [4]. Labral tearing may occur with repeated subluxations or a traumatic event in multidirectional instability [4].

History Taking

A thorough history and physical examination most often diagnose the degree, direction, frequency, and etiology of shoulder instability [13]. The history should define the mechanism of the injury, including the position of the arm, the amount of force applied, and the point of force application [162]. If the instability is recurrent, the history defines the initial injury, the position or action that results in instability, how long the shoulder stays out, whether radiographs are available with the shoulder out of joint, and what means have been necessary to reduce the shoulder [162]. The history also solicits evidence of neurologic or rotator cuff problems after previous episodes of shoulder instability [162]. Previous treatment of the recurrent instability, as well as the effectiveness of this treatment, should be documented in the history [162]. Note should be made of age at first dislocation, increasing ease of dislocation, frequency of recurrence, duration of symptoms, and patient's ability to reduce the dislocation himself or herself [158].

History taking for shoulder instability includes age, handedness, sport or recreational activity, unilateral or bilateral complaint, family history of shoulder dislocation, initial traumatic event, position of arm during subluxation or dislocation, number of previous episodes of dislocations or subluxations, whether the dislocation was reduced in the emergency department, interval of time between dislocation and reduction, degree of trauma required for recurrence, voluntary dislocation, dislocation during sleep, presence and location of pain, presence or absence of mechanical symptoms, sensory disturbance or motor weakness, and previous shoulder surgery [153]. In throwers, a detailed history with the chronology of symptoms is essential [231]. Pitchers commonly complain of loss of pitch control and loss of velocity and also describe symptoms distant from the shoulder joint [231]. The throwing phase in which the pain occurs gives direct clues to the underlying pathoanatomy [231]. Pain during cocking is often a result of instability or internal impingement with a type II SLAP lesion [231]. Pain during follow-through arises from rotator cuff or posterior capsular problems [231].

Swimmers will often complain of pain during the catch or the recovery, when the shoulder is more often in the provocative impingement position [231]. In swimmers, instability is often the principal culprit, exacerbating symptoms of impingement [231]. Symptoms elicited with the arm in adduction and internal rotation may suggest posterior instability [231]. Symptoms reproduced by holding objects with the arms at the sides often indicate inferior instability [231]. The location of pain or instability, its duration, and response to prior treatment should be noted for all athletes [231]. A focused history and physical examination, including the jerk, Kim, and posterior load shift tests, and a high index of suspicion can reveal the diagnosis of posterior instability [68]. Volitional dislocation of the shoulder must be ruled out in the history for posterior instability [14]. The diagnosis of each type of shoulder instability is made on the basis of a careful history and clinical examination followed by arthroscopy and, when necessary, functional electromyography [78]. The history takes account of the degree of trauma required to cause the first dislocation and whether the displacement was complete and requiring formal reduction or incomplete and spontaneously reducing [78].

An informed treatment decision should be guided by a thorough history and physical, careful examination of radiographs and MRI, and a discussion of the patient’s activity goals including, potentially, the timing of athletic seasons [31]. A thorough clinical exam is the most important factor when determining indication for shoulder instability surgery [24]. Clustering of thorough history and physical examination findings may identify those with posterior glenohumeral instability and assist in developing management strategies [112]. Detailed and specific information about prognosis is critical in the management of a first-time anterior dislocation [38]. The diagnosis of shoulder instability can be very easy when the patient presents with an appropriate history of trauma [69]. With the increasing availability of sports trainers, reduction of a dislocation by those personnel results in a history only, with no ED records or radiographs [69]. A more challenging problem occurs in patients with a sense of slipping and looseness in their shoulder without a history of macrotrauma [69]. This more subtle instability pattern is associated with a nondescript level of discomfort and diffuse pain around the shoulder girdle [69]. The discomfort is poorly localized and may be more scapular in location [69]. The physician must carefully inquire about which activities and arm positions provoke the symptoms [69].

The goal of clinical evaluation is to carry out an evaluation of the patient that leads to a reasonable management plan [44]. The four P’s that determine the outcome of treatment are the patient, the shoulder problem experienced, the procedure to treat the patient and the problem, and the physician rendering the treatment [44]. It is more important to know what patient a disease has than what disease the patient has [44]. A patient with posterior instability may respond with "I can't do my job," "I need more pain medicine," "My lawyer sent me," or "My shoulder keeps on slipping out when I lift something in front of me" [44]. The examiner should ask "What does your shoulder problem keep you from doing? When does it bother you the most?" [44]. The examiner should ask "How and when did that problem start?", "How much force was applied to your shoulder in the injury?", and "Tell me about the treatment you’ve had for it up to now." [44].

Investigations

Clinical Assessment: A thorough clinical examination is the most important factor when determining the indication for shoulder instability surgery [24]. Diagnostic practices vary significantly, with high variety observed in the use of diagnostic tools [19] and substantial variability in what is considered important in radiological reports for anterior shoulder instability, regardless of imaging modality [25]. Recurrent posterior shoulder instability is an uncommon condition that is often unrecognized, leading to incorrect diagnoses and delays [33]. Posterior shoulder dislocation is a rare and challenging injury with varied mechanisms of trauma that complicate diagnosis [40]. Simultaneous bilateral posterior shoulder dislocation is a rare entity that requires careful clinical and radiological evaluation, often necessitating CT scans for diagnosis [314].

Plain radiography: Conventional radiography remains the initial imaging study for evaluating patients with persistent shoulder pain and instability [201]. The standard shoulder series should include orthogonal views, including a true AP view in the scapular plane, an AP view, an axillary view, and a scapular Y view [157]. The axillary view is necessary for evaluating glenohumeral joint instability and enables determination of the humeral head position in the glenoid fossa [157]. It may detect occult, locked posterior shoulder dislocation in a patient who exhibits a lack of passive external rotation [157]. Specific views are indicated for targeted assessment: the West Point view for anterior glenoid bone loss, the Stryker notch view for Hill-Sachs lesions after dislocation, and the apical oblique view for glenoid rim fracture in instability [157]. Radiography can be used for screening patients for significant glenoid bone loss [301]. However, CT and MRI (2D or 3D) accurately measure glenoid bone loss in anterior shoulder instability, whereas radiographs do not [263]. Bone defects seen in preoperative plain radiographs are less important and more accurate imaging is needed to reveal their true role for recurrence of instability [313]. In patients with suspected posterior glenohumeral instability, imaging of the affected shoulder can show abnormalities of the bone, labrum, and joint capsule [290].

CT: CT with three-dimensional reconstructions is the advanced imaging study of choice for determining the extent of glenoid bone loss in the setting of shoulder instability [157]. Despite the advantages of MRI in the detection of soft tissue damages in recurrent anterior shoulder instability, CT imaging proved to be more important for glenoid defects [257]. CT and MRI (2D or 3D) accurately measure glenoid bone loss in anterior shoulder instability [263]. Advanced imaging modalities are essential for identifying associated lesions, and bony reconstruction procedures should be considered for patients with significant glenoid bone loss or recurrent instability after soft tissue reconstruction [246].

MRI: Magnetic resonance arthrography has been firmly established as the imaging modality of choice for demonstrating specific soft tissue abnormalities associated with glenohumeral instability [201]. It is regarded as the gold-standard imaging modality for shoulder instability [234] and is identified as the main tool in diagnosing shoulder instability injuries [271]. Magnetic resonance arthrography was an accurate method to assess accompanying lesions in first-time and recurrent anterior dislocation of the shoulder [252]. Magnetic resonance angiography has a high sensitivity when used to identify associated injuries in shoulder dislocation, although arthroscopy identified an additional injury in 8 patients (13%) [283]. Routine MRI has similar diagnostic value to MR arthrogram for measuring labral tear extent up to approximately 2 weeks postacute shoulder dislocation, after which it significantly loses accuracy and precision [305]. Patients who undergo MRI greater than 6 months from the time of primary shoulder dislocation demonstrate a greater incidence and severity of intra-articular pathology including SLAP tears, posterior labral tears, and anterior glenoid cartilage damage [292]. Capsular injury is commonly seen in magnetic resonance imaging of patients with anterior shoulder instability [240]. MRI is a valid imaging tool to diagnose and measure osseous lesions of the shoulder [310]. ZTE MRI demonstrated high reproducibility for the evaluation of glenoid bone defect in shoulders with anterior instability [307]. An increased glenoid index measured on MRI may help identify patients at risk for primary or recurrent anterior glenohumeral instability events and may help with guiding treatment and prevention [256]. Patients with multidirectional instability demonstrated quantifiable dynamic instability on cine MRI with significantly greater humeral head deviation and faster deviation velocity than healthy controls [309]. The superior-capsular elongation and its diagnostic criteria of measurements by MR arthrography could serve as references for diagnosing atraumatic posteroinferior shoulder instability [303]. Identification of critical radiographic variables on magnetic resonance arthrography assists in the accurate diagnosis and management of clinically significant posterior shoulder instability [37]. Even without posterior instability complaints or findings, posterior labral tears should be considered in patients with posterior shoulder pain during daily activities or sports, even when MRI or MRA findings are ambiguous [297]. Posterior HAGL lesions identified on radiographic imaging are not clinically significant unless the patient has symptoms and a history specific for posterior instability [311]. The current literature supports a variety of different imaging modalities that provide clinically acceptable accuracy in diagnosing and quantifying Hill-Sachs lesions, as well as determining whether they will cause persistent anterior shoulder instability [41].

Other Imaging Modalities: Ultrasonography is a low-cost alternative to MRI and arthrography for evaluating both skeletal and soft-tissue structures of the shoulder [151]. It is highly operator dependent and is not as useful for evaluating labral tears or rotator cuff tears that are very small or larger than 3 cm [151]. Arthrotomography of the glenoid labrum is a helpful adjunct in substantiating the diagnosis of shoulder instability and in planning the choice of surgical reconstruction [312].

Other Considerations: Overall, 3D MRI is a validated and reliable alternative to 3D CT for preoperative evaluation of static glenohumeral bone loss and dynamic morphological variables in shoulder instability [287, 288]. In the future, CT is expected to be superseded by MRI in anterior shoulder instability [289].

Treatment

Non-Operative

Nonsurgical management remains the primary strategy for atraumatic shoulder instability, with physiotherapy serving as the cornerstone of treatment regardless of the presence of structural pathology [253]. Approximately 80% of patients with atraumatic instability respond to non-operative measures [253]. For multidirectional instability (MDI), extensive physical therapy for 6 to 9 months is required before surgical consideration [4]. In cases of posterior instability with minimal symptoms, nonsurgical treatment including physical therapy, activity modification, and anti-inflammatory agents is indicated [68]. Following a single traumatic posterior shoulder injury, the arm should be immobilized in neutral rotation with the elbow in adduction for 1 to 2 weeks before initiating therapy [14]. Nonsurgical management of anterior instability typically involves brief sling immobilization (3 to 7 days) followed by structured rehabilitation focusing on cryotherapy, range of motion restoration, periscapular and rotator cuff strengthening, and sport-specific drills [31]. NHL team physicians strongly favor nonoperative management in-season for initial posterior instability events [224].

However, nonoperative treatment carries significant risks and costs. Primary non-operative management is a prominent risk factor for recurrence in young and adolescent athletes [125]. Recurrence rates for anterior instability can reach 86.7% in high-risk patients treated nonoperatively after their first incident [239]. Nonoperative treatment also incurs substantial societal costs [205]. Recent studies continue to demonstrate a role for nonoperative treatment in the successful long-term management of anterior glenohumeral instability [214].

Operative

Indications: Surgical intervention is contraindicated for voluntary posterior dislocators due to an extremely high failure rate [68]. For anterior instability, surgical treatment results in reduced rates of recurrence compared with nonsurgical treatment at 10-year follow-up [45]. Early arthroscopic stabilization after initial anterior dislocation is associated with a low 10-year recurrence rate of 35% compared to non-operative management [248]. Early operative stabilization of Bankart lesions in young patients significantly reduces the risk of recurrent instability [258]. Arthroscopic lavage reduced the recurrence rate and produced better functional outcomes at 1-year follow-up than non-operative treatment in young individuals with traumatic primary anterior dislocation [265]. Successful results have been obtained in patients younger than 40 years with both primary and recurrent anterior instability after arthroscopic treatment [167]. For posterior instability, surgical stabilization is not indicated in all athletes after a first episode [235]. A thorough clinical exam is the most important factor in determining surgical indication, with no difference in outcomes based on radiologist-reported magnetic resonance arthrogram findings [24].

Surgical Approach / Technique: Arthroscopic anterior capsulolabral repair is the most common surgical technique in North America, accounting for more than 90% of surgical cases for anterior shoulder instability [31]. Isolated arthroscopic soft-tissue stabilization is best suited for patients with little to no glenoid bone loss, minimal humeral bone loss, and good capsular and labral tissue quality [31]. The indications for an isolated soft-tissue procedure are now narrower, with the ideal candidate presenting with minimal glenoid bone loss (13.5%) [54]. The open Bankart procedure typically involves a pants-over-vest capsular shift in addition to labral repair [31]. A humeral avulsion of the glenohumeral ligaments (HAGL) typically warrants an open repair with anchors back to the humeral neck [31]. For posterior instability, the benchmark treatment when nonsurgical treatment fails is an anchor-based arthroscopic capsulolabral repair [68]. Arthroscopic techniques for posterior instability repair have shown promising results, generally more favorable than those after anterior instability repair [16]. The presence of a posterior glenoid fracture (bony Bankart lesion) is not a contraindication to arthroscopic shoulder stabilization [242]. For MDI, arthroscopic pancapsular plication ± rotator interval closure is a standard technique [4]. To avoid asymmetric tightening, capsulorrhaphy should address inferior redundancy in a balanced fashion [4]. Arthroscopic and open capsular shifts have been successful in restoring stability and decreasing pain in MDI [13]. The inferior capsular shift procedure demonstrates efficacy and durability for MDI [120]. A modified capsular shift procedure is effective for atraumatic anterior-inferior shoulder instability [186].

Bone Loss Management: The success of treating anterior glenohumeral instability relies on multiple factors, including glenoid bone loss [152]. Recurrent anterior shoulder instability with glenoid bone loss requires restoring the bone [152]. In the interim, surgical soft-tissue stabilization might be more aggressively indicated in cases of primary shoulder dislocation, whereas recurrent instability with bone loss should be referred to experienced high-volume specialists [79]. The Latarjet is a safe and effective procedure for patients with shoulder instability [155]. Current evidence supports the safety and efficacy of both the Latarjet and free bone block (FBB) procedures for anterior shoulder stabilization in the presence of glenoid bone loss [198]. A dynamic anterior stabilization procedure using buttons demonstrated effectiveness and safety, being a viable option for treating anterior shoulder instability with glenoid bone loss of less than 20% [199]. Beyond 20% posterior bone loss, an isolated labral repair cannot restore adequate shoulder stability [68]. The iliac posterior shoulder bone-block is effective in managing instances of involuntary posterior shoulder instability, showing satisfactory results in terms of non-recurrence, pain relief, and function recovery [264].

Outcomes and Complications: A meta-analysis of 22 studies found no difference in rates of recurrent instability or patient-reported outcomes between open and arthroscopic anterior stabilization techniques [31]. However, if the definition of recurrent instability is extended beyond frank dislocations to include apprehension and subluxations, open repairs outperform arthroscopic repairs [31]. Failure rates in contact athletes are lower with open repairs than with arthroscopic repairs, based on nonrandomized data [31]. In a randomized clinical trial comparing open versus arthroscopic Bankart repair, an increased rate of recurrence was noted after arthroscopic repair (23% versus 11% in open repair) [156]. The highest rate of recurrence in this trial was noted in males younger than 25 years with Hill-Sachs lesions [156]. A systematic review of more recent meta-analyses demonstrated no difference in recurrence between open and arthroscopic anterior stabilization techniques [156]. There is insufficient evidence from randomised trials comparing arthroscopic with open surgery for treating anterior shoulder instability [255]. There was no evidence regarding the effectiveness of surgical management for post-traumatic chronic shoulder instability in a network meta-analysis [232]. A large 2017 cohort study showed subjective instability in 62% and revision surgery in 32% of patients undergoing arthroscopic Bankart repair after multiple episodes of instability, rates that were fourfold higher than in first-time dislocators [31]. Arthroscopic stabilization for recurrent anterior shoulder instability can be performed safely, with clinical outcomes comparable to those after traditional open stabilization [168].

For posterior instability, recurrent instability rates for posterior stabilization are low (8%), and 90% of patients return to sport [68]. In throwers, only 58% were able to return to sport at the same level after posterior stabilization [68]. Revision surgery is only required in 6% of patients with posterior instability, and the outcomes are far inferior to those of index surgery, with only 15% returning to sport at their preoperative level [68]. Arthroscopic treatment of posterior shoulder instability is an effective means to improve symptoms associated with recurrent posterior subluxation [184]. Arthroscopic stabilization of posterior shoulder instability resulted in good outcomes with high patient satisfaction and low rates of recurrent instability, revisions, and residual pain [192]. Primary arthroscopic treatment of posterior shoulder instability is associated with favorable outcomes and high return to sport and work rates [166]. Treatment of posterior shoulder instability by capsulolabral reconstruction leads to good clinical outcomes; however the recurrence rate is high [148]. In a prospective cohort study of 200 shoulders in 183 athletes who underwent arthroscopic posterior capsulolabral repair, results were durable at 3 years with 90% of athletes returning to sport [16].

For MDI, recurrence is 7% for both open and arthroscopic techniques [4]. Axillary nerve injury, stiffness (rare), and subscapularis insufficiency (after open procedure) are complications of MDI surgery [4]. Thermal capsulorrhaphy has recently shown a high complication rate for MDI [13]. The results of arthroscopic treatment are less predictable in patients with greater than 2+ instability in two or more directions, patients with 3+ (locking) unidirectional patterns without evidence of capsular injury, and those with atraumatic posterior instability [13]. An open capsular shift may provide a more predictable outcome than arthroscopic treatment for patients with greater than 2+ instability in two or more directions, 3+ (locking) unidirectional patterns without capsular injury, or atraumatic posterior instability [13]. Adolescent multidirectional shoulder instability refractory to non-surgical management appears to have long-term outcomes after surgical intervention that are comparable to adolescent patients with unidirectional instability [179]. Surgical procedures for atraumatic shoulder instability should be individualised and address each patient's pathology rather than relying on one procedure for all [253]. An experienced multidisciplinary team is essential to maximize success in surgical interventions for atraumatic shoulder instability [253]. Successful treatment of anterior instability of the shoulder requires a balance between restoring joint stability and minimizing loss of glenohumeral motion [174].

Rehabilitation and Return to Play: Postoperatively, the shoulder should be placed in a rigid immobilizer with the arm abducted to 30° in neutral rotation for posterior instability [14]. After a short period of immobilization for posterior instability, ROM exercises may begin, and strengthening should begin at 12 weeks [14]. The pooled published rate of return to any sport after posterior instability surgery is 91%, and to preinjury level of sport is 67% [14]. Postoperative rehabilitation protocols for anterior instability typically include a period of immobilization in a sling for 3 -4 weeks [269]. Pendulums exercises are begun immediately after anterior instability surgery [269]. Active assisted range of motion exercises, external rotation (0 -30°) and forward flexion (0 -90°) are begun immediately after anterior instability surgery [269]. From weeks six to twelve after anterior instability surgery, active and active assisted motion is emphasized to re-establish full range of motion [269]. Strengthening is begun once full, painless, range of motion has been restored after anterior instability surgery [269]. Sports specific exercises are started around 16 -20 weeks post-surgery for anterior instability [269]. Patients may return to contact sports at 20 and 24 weeks following Latarjet and arthroscopic stabilization respectively [269]. In open procedures where the subscapularis is incised, active internal rotation and passive external rotation is avoided while the subscapularis heals [269].

In a specific protocol for anterior instability, the shoulder was placed in a sling for 3 weeks, while allowing nonresisted activities of daily living without elevation of the shoulder [251]. Patients immediately began physiotherapy, which continuously increased in intensity over the next 9 weeks after anterior instability surgery [251]. Return to contact in training was allowed after 12 weeks, whereas return to full contact and competition usually would follow within the next 3 months, depending on the progress of physiotherapy [251]. Similar protocols apply for patients older than 40 years, with a 3-week sling period, immediate physiotherapy increasing over 9 weeks, return to training after 12 weeks, and full contact within the next 3 months [267]. For SLAP tears, the shoulder was placed in a sling for 3 weeks, while allowing non-resisted activities of daily living without elevation of the shoulder [238]. Patients immediately began physiotherapy, which continuously increased in intensity over the next nine weeks after SLAP tear repair [238]. Return to contact in training was allowed after twelve weeks, while return to full contact and competition usually would follow within the next three months, depending on progress of physiotherapy [238]. For radiofrequency capsular shrinkage for voluntary shoulder instability, the arm was placed in a sling for comfort for a few days [254]. Motion was allowed, avoiding extremes in all directions for the first 6 weeks after radiofrequency capsular shrinkage [254]. Proprioceptive physiotherapy was initiated within the first week after surgery for radiofrequency capsular shrinkage [254].

Setting of Care: Post-operative protocols are in widespread use across the UK with 93.5% of participants reporting their use [245]. Three quarters (75%) of UK participants have a single protocol that is used by all surgeons and physiotherapists [245]. In most cases (72.1%) UK post-operative protocols were jointly written between surgical and physiotherapy teams [245]. Immobilisation of the shoulder following arthroscopic stabilisation was reported as routine by 79.9% of UK respondents [245]. A cross body sling was the most common position of immobilisation (63.4%) in UK practice [245]. The duration of immobilisation reported in UK practice varied, ranging from less than 48 hours to up to 6 weeks [245]. Over half (53.6%) of UK protocols allowed for patients to commence passive movement either immediately or as soon as they felt able [245]. This rises to 60% for commencing active-assisted movement in UK protocols [245]. The British Elbow and Shoulder Society (BESS) guideline is designed to be accessible to clinicians without specialist knowledge, thereby enhancing its uptake in practice [227]. The components included in the BESS rehabilitation protocols represent the minimal standard of care in rehabilitation [227]. While the BESS protocols provide a detailed illustration of the recommended rehabilitation principles and examples of exercises using a structured framework, they are not intended to be prescriptive [227]. Additional factors, such as clinician and patient preference and functional demand, should be considered when appropriate in BESS rehabilitation [227]. The work for the BESS guideline was undertaken under BESS oversight with contributions from orthopaedic surgeons, shoulder specialist physiotherapists, and patient representatives [227]. In post-operative rehabilitation for traumatic anterior shoulder dislocation, substantial variability exists in duration of sling use, timescale to begin movements and criteria to return to sport [227].

Complications

Recurrence and Failure of Stabilization

Recurrent instability remains a significant risk following surgical stabilization. Following primary arthroscopic anterior capsulolabral repair, recurrent instability was observed in 30% of patients at midterm follow-up [29]. In a US epidemiologic population of patients younger than 40 years old, the rate of recurrent anterior shoulder instability was roughly one-third after initial physician consultation [262]. Long-term data indicate that approximately one third of shoulders stabilized with suture anchors experienced at least one redislocation after 8 to 10 years [55]. For patients undergoing arthroscopic capsulolabral revision repair for recurrent anterior shoulder instability, the recurrent instability rate was 27.6% at a minimum 20-year follow-up [80]. A history of multiple instability episodes prior to presentation is the greatest predictor of recurrent instability, failure of nonoperative treatment, and progression to surgery [73]. Additionally, recurrent instability requiring capsular reconstruction seems to be more prevalent in patients with a previous history of shoulder dislocation [243]. Preoperative risk factors for recurrent anterior glenohumeral instability following a primary Latarjet procedure include a history of bilateral shoulder instability and an atraumatic mechanism of dislocation [260]. The natural history of first-time shoulder dislocations is bound up with arthropathy [65].

Nerve Injury

Axillary nerve injury is a recognized complication of multidirectional instability surgery [4]. In the context of total shoulder arthroplasty, most nerve injuries are neurapraxias that recover with time [250]. Nerve injuries resulting from interscalene blocks can be permanent [27].

Stiffness and Frozen Shoulder

Stiffness is a rare complication of multidirectional instability surgery [4]. Some risk of recurrent instability is part of the natural history of anterior shoulder dislocation, which can be managed with manipulation under anaesthesia and injection for secondary frozen shoulder [50].

Arthropathy and Joint Degeneration

The incidence of shoulder arthropathy in patients with shoulder instability is difficult to measure due to the long time period between dislocation and arthritis [75]. Arthroscopic evaluation within 10 days of first-time traumatic dislocations revealed osteochondral lesions of the humeral head in 34 of 63 patients and chondral lesions in an additional 23 of 63 patients [75]. In a separate series of 24 patients with first-time anterior shoulder dislocation assessed arthroscopically 1 to 3 days after injury, osteochondral lesions were found in six shoulders, while all 18 remaining shoulders had chondral lesions [75]. In a series of 422 patients with shoulder instability, 24% of those with acute instability had grade I or higher chondral lesions, and 12% had Grade III or IV chondral damage [75]. The degree of arthropathy 33 to 35 years after the Bristow-Latarjet repair seems to follow the natural history of shoulder dislocation with respect to arthropathic joint degeneration [83]. Misplaced suture anchors can give rise to secondary degenerative joint disease or "anchor arthropathy," as suture anchors that are prominent on the glenoid surface can excoriate the humeral articular cartilage [27].

Hardware and Implant Complications

Intra-articular infusion of local antibiotics via a pain pump after arthroscopic instability repairs results in a risk of glenohumeral chondrolysis [27]. The routine use of bone transfers for glenohumeral instability in the absence of major glenoid bone loss is not advisable due to increased risk of arthritis, screw-related problems, damage to the subscapularis, and difficulty in revision [27]. The Latarjet procedure for anterior shoulder instability results in an overall complication rate of 16.1% and a reoperation rate of 2.6% [206]. Serious complications at short-term follow-up after the Latarjet procedure appear rare [206]. Female patients undergoing the Latarjet procedure showed similar 90-day complication and 2-year secondary surgery rates to a matched cohort of male patients [215]. Short-term outcomes for pre-shaped allograft for glenoid reconstruction are reassuring, but more research is needed to study long-term graft union, graft resorption, glenohumeral arthritis, and patient outcomes including recurrent shoulder instability [56].

Soft Tissue and Structural Complications

Subscapularis insufficiency is a complication after open procedures for multidirectional instability [4]. Open repair of anterior instability risks subscapularis insufficiency [28]. A torn subscapularis tendon is likely to be underreported and can contribute to anterior instability after shoulder arthroplasty [274]. One report suggested that lesser tuberosity osteotomy failure may be an underreported complication [274]. Progressive superior migration of the humeral head can result in loosening of the glenoid component [274]. Inferior instability after hemiarthroplasty for proximal humeral fractures is related to the loss of normal humeral height and inferior placement of the humeral head [274].

Arthroplasty-Specific Complications

Instability is the second leading cause of complications associated with shoulder arthroplasty, with a reported prevalence of 4% and accounting for 30% of all complications [274]. In a meta-analysis of 11 series of total shoulder arthroplasties that included 838 patients, the incidence of postoperative dislocation was 1.2% over a follow-up period of 20 to 54 months [274]. Approximately 80% of instability complications after total shoulder arthroplasty involve anterior or superior instability [274]. The overall complication rate after total shoulder arthroplasty is estimated to be approximately 15% [279]. Component loosening is the most commonly reported complication after total shoulder arthroplasty, occurring in 6.31% of all shoulders [250]. Instability is the second most commonly reported complication after total shoulder arthroplasty, occurring in 4.9% of all shoulders [250]. Periprosthetic fracture is the third most commonly reported complication after total shoulder arthroplasty, occurring in 1.8% of all shoulders [250]. Rotator cuff tear is the fourth most commonly reported complication after total shoulder arthroplasty, occurring in 1.3% of all shoulders [250]. Neural injury is a complication of total shoulder arthroplasty, occurring in 0.8% of all shoulders [250]. Infection is a complication of total shoulder arthroplasty, occurring in 0.7% of all shoulders [250]. Complications after total shoulder arthroplasty tend to occur late in the postoperative course, with component loosening reported at approximately 8 years, infection at 12 years, and periprosthetic fractures at 6 years [279]. Reverse total shoulder arthroplasty initially resulted in relatively high complication rates of 50% [279]. The complication rate for reverse total shoulder arthroplasty has fallen to 6% recently reported [279]. The most common complications after reverse total shoulder arthroplasty are scapular notching, hematoma formation, glenoid dissociation, glenohumeral dislocation, acromial and scapular spine fractures, infection, loosening or dissociation of the humeral component, and nerve injury [279].

Other Considerations

Patients with a history of shoulder instability or replacement are at risk for shoulder dislocation during common elbow and hand procedures [230].

Recovery

Rehabilitation protocol: The cornerstone of treatment for shoulder instability remains immobilization followed by rehabilitation [13]. For anterior shoulder instability, adequate nonsurgical treatment typically involves a brief period of sling immobilization (3 to 7 days), followed by structured rehabilitation focusing on cryotherapy, restoration of full range of motion, periscapular and rotator cuff strengthening, and stabilization and sport-specific drills [31]. Multidirectional instability (MDI) often manifests as bilateral shoulder subluxations in a susceptible patient and should be treated with an extended course of physical therapy [13].

Other Considerations: The optimal nonoperative treatment of a shoulder dislocation is still unknown and deserves further study [13]. Nonsurgical management for anterior shoulder instability is typically considered in preadolescents, patients older than 30 years, those with low activity demands, and in-season athletes [31]. Patients treated conservatively for anterior shoulder instability were far more likely to achieve a successful outcome defined as completing a subsequent season in their same sport compared to surgical patients [320]. Multiple episodes of instability have been linked to increased attritional glenoid bone loss, increased procedural complexity, increased severity of glenoid chondral defects, compromised outcomes at the time of surgical shoulder stabilization, and higher rates of glenohumeral osteoarthritis [31].

In the absence of severe capsular laxity or bony deficiency, arthroscopic stabilization is considered a first-line therapy in recurrent anterior and posterior instability of traumatic origin [13]. Early arthroscopic stabilization can decrease recurrence rates and improve functional outcomes in young (>25 years old), high-risk patients with first-time anterior dislocations and an associated Bankart lesion [13]. This study demonstrates a long-term benefit in overall shoulder stability and functional outcome in high-risk patients who have undergone arthroscopic Bankart repair for first-time anterior dislocation [61]. Participation in a contact sport is not a contraindication to arthroscopic stabilization [13]. Athletes may return to play after a shoulder dislocation or after stabilization surgery when strength and mobility have normalized [13].

With a follow-up of 97%, about one third of the stabilized shoulders experienced at least one redislocation after 8 to 10 years following arthroscopic shoulder stabilization using suture anchors [55]. At midterm follow-up, recurrent shoulder instability following primary arthroscopic anterior capsulolabral repair was 30% in this series [29]. Arthroscopic repair for posterior shoulder instability yields favorable mid-term outcomes, with significant improvements in functional scores and a low recurrence rate at a mean follow-up of 10.6 years [219]. The combination of arthroscopic remplissage in addition to the classic Bankart repair for recurrent anterior shoulder instability with engaging Hill–Sachs lesions has long-term outcomes in terms of the recurrence rate and does not significantly influence the range of motion of the shoulder [221].

The open Latarjet procedure is a safe and reliable technique for recurrent anterior shoulder instability, as demonstrated by long-term follow-up studies [70, 71]. Long-term data suggest that the benefits of the Latarjet procedure are durable, and it should be considered as a viable and reliable treatment option for anterior glenohumeral instability [74]. The number of episodes of dislocation before surgery and the delayed surgical intervention did not increase the recurrent anterior shoulder instability rates postoperatively following an open Latarjet-Bristow procedure [317]. In a series of open shoulder anterior capsular reconstruction for instability from severe capsular deficiency, 9 shoulders (45%) remained completely stable at 3.8 years [315].

Patients with a history of anterior shoulder instability undergoing total shoulder arthroplasty can expect continued improvement in function compared with preoperative values at mid-term follow-up [64]. Shoulder arthroplasty in the setting of prior anterior instability results in improved subjective and functional outcome scores that are comparable to patients without a history of instability [321].

In a cohort of young patients undergoing arthroscopic surgery for posterior shoulder instability, there was no significant difference in reoperation rate and recurrence of symptoms between athletes who underwent objective return to sport testing and those who were released to sport on a time-based protocol [318, 319]. Arthroscopic and open capsular shifts have been successful in restoring stability and decreasing pain for MDI, but thermal capsulorrhaphy has recently shown a high complication rate [13]. Generally, the results of arthroscopic treatment are less predictable in patients with greater than 2+ instability in two or more directions, patients with 3+ (locking) unidirectional patterns without evidence of capsular injury, and those with atraumatic posterior instability [13]. In patients with greater than 2+ instability in two or more directions, 3+ (locking) unidirectional patterns without evidence of capsular injury, or atraumatic posterior instability, an open capsular shift may provide a more predictable outcome [13].

Regardless of age, glenohumeral posttraumatic arthritis developed in two-thirds of patients by the end of the 25-year period following anterior shoulder instability [31]. The natural history of the first time shoulder dislocations is bound up with arthropathy [65]. Some risk of recurrent instability is part of the natural history of anterior shoulder dislocation [50]. Radiographic progression of glenohumeral arthritis occurred in 14% of patients with posterior shoulder instability [87]. The incidence of first-time anterior shoulder instability in patients aged 50 years or older was 28.8 per 100,000 person-years [81]. Patients aged >50 years with anterior shoulder instability have a decreased risk of recurrent dislocation after operative treatment compared with non-operative treatment [73].

Key Evidence

• [L5] [1] (10.1177/17585732251320070)
• [L4] The MOON Shoulder Instability Study has enrolled the largest cohort of patients undergoing shoulder stabilization to date. [2] (10.1177/0363546518755752)
• [L5] The authors propose a classification system, which challenges previous systems by being all inclusive and recognises that more than one pathology can occur in an individual shoulder. [5] (10.1016/j.cuor.2004.04.002)
• [L3] Long-term follow-up demonstrates that nearly 40% of patients treated non-operatively for posterior shoulder instability eventually require surgery. [7] (10.1177/2325967118s00098)
• [L4] At long-term follow-up of 17 years, a high rate of poor outcomes was observed following nonoperative management of anterior shoulder instability. [8] (10.1016/j.jse.2021.07.016)
• [L4] This highlights the need for a consensus on definition of recurrence across shoulder instability studies. [9] (10.1016/j.asmr.2021.02.002)
• [L5] Proper evaluation of bone loss best determines shoulder instability surgical indications and outcomes. [10] (10.1016/j.arthro.2021.01.004)
• [L3] The 1-year outcomes in this prospective study suggest superiority of operative over non-operative treatment for posterior shoulder instability. [11] (10.1016/j.otsr.2017.08.004)
• [L2] More than a third of continuous outcomes in anterior shoulder instability trials had a continuous fragility index less than the reported loss to follow-up. [12] (10.1177/03635465231202522)
• [L1] The early and midterm results of arthroscopic stabilization of the shoulder for posterior instability are promising. [15] (10.1016/j.arthro.2014.11.009)
• [L3] Most patients younger than 40 years with shoulder instability who were initially treated nonoperatively for 6 months were definitively treated without surgery. [17] (10.1016/j.arthro.2021.03.047)
• [L4] This review evaluates existing data on the presentation of shoulder instability in men and women to determine if there are differences in occurrence, treatment, or functional outcome following management. [18] (10.2106/jbjs.rvw.19.00007)
• [L4] Many different diagnostic examinations for assessing shoulder instability are used and a high variety is seen in the use of diagnostic tools. [19] (10.1007/s00402-016-2443-7)
• [L5] The consensus statement aims to improve diagnosis and treatment of shoulder instability through universal agreement on outcome measurement tools and tailored treatment based on pathology, patient age, activity demands, and surgeon skills. [20] (10.1016/j.arthro.2009.06.022)
• [L4] Biomechanical studies on posterior shoulder instability remain limited in the literature, with current models performed in a static manner which limits their translation for explaining a dynamic pathology. [21] (10.5312/wjo.v9.i11.245)
• [L5] Failure of primary shoulder stabilization procedures is often related to uncorrected anatomic pathology, and the instability severity index score permits precise identification of patients at risk. [22] (10.1016/j.arthro.2010.11.057)
• [L5] The Delphi method is a structured communication technique used to allow a panel of experts to achieve a consensus in a systematic manner, resulting in an international consensus statement on shoulder instability covering diagnosis, nonoperative management, surgical options, rehabilitation, and clinical follow-up. [23] (10.1016/j.arthro.2021.11.052)
• [L3] A thorough clinical exam is the most important factor when determining indication for shoulder instability surgery. [24] (10.1016/j.xrrt.2026.100675)
• [L5] Substantial variability was observed in the scoring of important elements in the radiological report for the evaluation of anterior shoulder instability, regardless of modality. [25] (10.1016/j.jseint.2024.03.012)
• [L3] At midterm follow-up, recurrent shoulder instability following primary arthroscopic anterior capsulolabral repair was 30% in this series. [29] (10.1016/j.arthro.2019.11.109)
• [L2] We recommend using it in following up patients with shoulder instability. [30] (10.1016/j.otsr.2016.10.024)
• [L5] Recurrent posterior shoulder instability is an uncommon condition often unrecognized, leading to incorrect diagnoses and delays. [33] (10.5435/00124635-200608000-00004)
• [L3] [36] (10.1016/j.jse.2024.01.043)
• [L3] Identification of these critical radiographic variables on magnetic resonance arthrography assists in the accurate diagnosis and management of clinically significant posterior shoulder instability. [37] (10.1177/0363546516660076)
• [L2] Detailed and specific information about prognosis is critical in the management of a first-time anterior shoulder dislocation. [38] (10.1016/j.jse.2010.10.037)
• [L4] They are considered safe and clinically effective for the management of anterior shoulder instability with glenoid bone loss. [39] (10.5435/jaaos-d-22-00837)
• [L4] Posterior shoulder dislocation is a rare and challenging injury with varied mechanisms of trauma that complicate diagnosis. [40] (10.5435/jaaos-22-03-145)
• [L1] The current literature supports a variety of different imaging modalities that provide clinically acceptable accuracy in diagnosing and quantifying Hill-Sachs lesions, as well as determining whether they will cause persistent anterior shoulder instability. [41] (10.1016/j.arthro.2020.08.005)
• [L3] [42] (10.1007/s00167-011-1552-7)
• [L5] An expanded assessment framework is useful to estimate the contribution of each component of non-traumatic shoulder instability and offer a framework for targeted rehabilitation, though the validity of testing specific subgroups remains to be established. [43] (10.1177/1758573214548934)
• [L1] Surgical treatment of primary, traumatic, anterior shoulder instability results in reduced rates of recurrence compared with nonsurgical treatment at 10-year follow-up. [45] (10.1016/j.arthro.2006.11.026)
• [L2] The FEDS classification, particularly the frequency and etiology of the patient's shoulder instability, may be helpful in identifying patients with a higher likelihood of undergoing surgical treatment. [46] (10.1177/2325967115607434)
• [L4] The thresholds defined in this study can provide a guideline for interpreting patient outcomes following arthroscopic stabilization for posterior shoulder instability, allowing for earlier detection of recurrent posterior instability. [49] (10.1016/j.jseint.2025.08.006)
• [L4] Some risk of recurrent instability is part of the natural history of anterior shoulder dislocation. [50] (10.1016/j.jor.2015.01.030)
• [L5] This paper reviews the nonoperative treatment and the postoperative management of patients with various classifications of shoulder instability. [51] (10.2519/jospt.2002.32.10.497)
• [Paper] The indications for an isolated soft-tissue procedure in anterior shoulder instability are now narrower; the ideal candidate presents with minimal glenoid bone loss (13.5%). [54] (10.2106/jbjs.rvw.26.00033)
• [L4] With a follow-up of 97%, about one third of the stabilized shoulders experienced at least one redislocation after 8 to 10 years. [55] (10.1177/0363546511415657)
• [Paper] Short-term outcomes are reassuring, but more research is needed to study long-term graft union, graft resorption, glenohumeral arthritis, and patient outcomes including recurrent shoulder instability. [56] (10.1016/j.eats.2017.10.007)
• [L2] RCTs reporting on shoulder instability surgery are well performed but poorly reported. [57] (10.1177/1758573218754370)
• [L5] [58] (10.1530/eor-24-0025)
• [L1] This study demonstrates a long-term benefit in overall shoulder stability and functional outcome in high-risk patients who have undergone ABR for first-time anterior dislocation. [61] (10.2106/jbjs.19.00858)
• [L3] At mid-term follow-up, patients with a history of anterior shoulder instability undergoing total shoulder arthroplasty can expect continued improvement in function compared with preoperative values. [64] (10.1016/j.jse.2023.07.005)
• [Abstract] The natural history of the first time shoulder dislocations is bound up with arthropathy. [65] (10.1016/j.jse.2007.02.100)
• [L3] This long-term follow-up study demonstrated that the open Latarjet procedure is a safe and reliable technique for recurrent anterior shoulder instability. [70] (10.1016/j.jse.2021.03.097)
• [L3] This long-term follow-up study demonstrated that the open Latarjet procedure is a safe and reliable technique for recurrent anterior shoulder instability. [71] (10.1007/s00402-020-03426-2)
• [L3] A history of multiple instability episodes prior to presentation was the greatest predictor of recurrent instability and failure of nonoperative treatment and progression to surgery. [73] (10.1016/j.asmr.2023.03.014)
• [L4] The long-term data suggest that these benefits are durable, and the Latarjet procedure should be considered as a viable and reliable treatment option for anterior glenohumeral instability. [74] (10.1016/j.jseint.2025.04.033)
• [L4] [75] (10.1016/j.csm.2004.08.010)
• [L4] There is substantial variability in outcome reporting for high-impact anterior shoulder instability literature with 28 different outcome tools used, making it difficult to compare outcomes between studies. [76] (10.1016/j.arthro.2016.07.027)
• [L5] [77] (10.1016/j.arthro.2024.04.035)
• [L5] In the interim, surgical soft-tissue stabilization might be more aggressively indicated in cases of primary shoulder dislocation, whereas recurrent instability with bone loss should be referred to experienced high-volume specialists. [79] (10.1016/j.arthro.2016.06.032)
• [L4] Patients undergoing ACRR for recurrent anterior shoulder instability had a recurrent instability rate of 27.6% at a minimum 20-year follow-up. [80] (10.1177/23259671251376528)
• [L3] The incidence of first-time anterior shoulder instability in patients aged 50 years or older was 28.8 per 100,000 person-years. [81] (10.1177/23259671221129301)
• [L4] The degree of arthropathy 33 to 35 years after the B-L repair seems to follow the natural history of shoulder dislocation with respect to arthropathic joint degeneration. [83] (10.1016/j.jse.2014.09.021)
• [L3] Radiographic progression of glenohumeral arthritis occurred in 14% of patients with posterior shoulder instability. [87] (10.1177/2325967118s00154)
• [L5] The biomechanical shoulder model is consistent with clinical observations. [89] (10.1016/j.jse.2016.05.031)
• [L4] The Latarjet procedure leads to anatomic and biomechanical changes in the shoulder. [104] (10.1016/j.asmr.2023.100804)
• [L4] Traumatic shoulder instability in the older patient may result in a wide array of pathologic findings as well as a diversity of clinical presentations. [105] (10.1177/2325967115584318)
• [L3] Patients do not always recognize anterior shoulder instability, and initial physical examination may be limited in the acute setting. [110] (10.1177/23259671251414851)
• [L4] Pain can serve as a clinical indicator of larger labral pathology in patients presenting with shoulder instability. [111] (10.1177/17585732251316476)
• [L4] Clustering of thorough history and physical examination findings, including the aforementioned tests, may identify those with posterior glenohumeral instability and assist in developing management strategies. [112] (10.1177/1941738117752306)
• [L5] The system categorizes instability based on frequency, aetiology, direction, and severity. [113] (10.1136/bjsm.2009.071183)
• [L5] The findings of this study clearly indicated that shortening of the clavicle affects the kinematics in the shoulder girdle. [116] (10.1177/0363546509355143)
• [L2] Primary non-operative management is a prominent risk factor for recurrence of shoulder instability. [125] (10.1136/bjsports-2016-096895)
• [L4] The PHAGL lesion is challenging to diagnose clinically and can be the cause of posterior instability or a component of the spectrum of shoulder instability. [127] (10.1016/j.arthro.2007.02.006)
• [L1] Shoulder instability cannot reliably be classified using the ICD-9 coding system. [131] (10.1016/j.jse.2008.10.005)
• [L3] Microinstability is diagnostically challenging and can be diagnosed in young patients with ambiguous shoulder pain during motion, without instability. [132] (10.1007/s00167-022-06941-4)
• [Paper] HAGL lesions are a rare and underdiagnosed cause of anterior shoulder instability that can lead to recurrent dislocations if unaddressed. [135] (10.1016/j.eats.2020.10.053)
• [Paper] GAGL lesions are an uncommon cause of anterior shoulder instability and require a high level of suspicion. [137] (10.1016/j.eats.2019.06.001)
• [L4] Recurrent anterior instability of the shoulder is a complex disorder which mainly affects younger population, and generally requires surgical intervention to restore joint stability. [140] (10.12998/wjcc.v2.i11.676)
• [L3] In this series of anterior shoulder instability in children and adolescents, instability lesions varied significantly by age, with atypical lesions more common in patients <15 years of age and bone loss associated with older age at presentation. [143] (10.1177/03635465231171129)
• [L5] Capsular repair also significantly alters normal glenohumeral kinematics. [147] (10.1007/s00167-015-3915-y)
• [Paper] Treatment of posterior shoulder instability by capsulolabral reconstruction leads to good clinical outcomes; however the recurrence rate is high. [148] (10.1016/j.otsr.2017.08.002)
• [L5] Biomechanical changes of passive glenohumeral joint motion occur in the glenohumeral joint with as little as 5% GIRD. [149] (10.1177/0363546512462012)
• [L5] Tears of the subscapularis have greater biomechanical consequences than do tears of the infraspinatus. [150] (10.1016/j.arthro.2009.09.007)
• [L5] The success of treating anterior glenohumeral instability relies on multiple factors, including glenoid bone loss. [152] (10.1016/j.arthro.2021.09.002)
• [L5] Simulated anterosuperior rotator cuff tears involving the superior half of the subscapularis significantly alter shoulder biomechanics and lead to increased anterosuperior and superior glenohumeral translation under higher loads. [154] (10.1016/j.arthro.2008.10.005)
• [L1] The Latarjet is a safe and effective procedure for patients with shoulder instability. [155] (10.1177/1758573220945318)
• [L4] Clavicle shortening of >10% greatly affects scapular kinematics in vivo. [163] (10.1016/j.jse.2017.03.013)
• [L5] In the setting of shoulder instability without evidence of a labral tear, the capsulolabral advancement technique may be considered biomechanically superior. [165] (10.1016/j.arthro.2012.04.140)
• [L1] Primary arthroscopic treatment of posterior shoulder instability is associated with favorable outcomes and high return to sport and work rates. [166] (10.1016/j.asmr.2024.101032)
• [L3] Successful results were obtained in patients younger than 40 years with both primary and recurrent anterior shoulder instability after arthroscopic treatment. [167] (10.1016/j.jse.2023.05.029)
• [L1] Arthroscopic stabilization for recurrent anterior shoulder instability can be performed safely; the clinical outcomes are comparable to those after traditional open stabilization. [168] (10.1177/0363546506288239)
• [L5] The ABC classification distinguishes three groups of posterior glenohumeral instability with two different subtypes based on the pathomechanical type of instability and the current standard of treatment. [170] (10.1007/s11678-017-0404-6)
• [L3] Glenohumeral decentering is significantly associated with diminished shoulder function and active range of motion in all planes. [172] (10.1016/j.jse.2025.03.038)
• [L5] Successful treatment of anterior instability of the shoulder requires a balance between restoring joint stability and minimizing loss of glenohumeral motion. [174] (10.1177/03635465030310011001)
• [L3] Arm kinematic analyses suggest that open surgery stabilizes the shoulder but does not necessarily restore normal movement quality. [175] (10.1016/j.jse.2013.09.021)
• [L5] Partial-thickness articular-sided rotator cuff tears with a thickness >50% involving the rotator cable increased glenohumeral translation and changed kinematics in our cadaveric biomechanical model. [176] (10.1016/j.jse.2016.12.063)
• [L5] The trapezoid and conoid ligaments have unique functions in normal shoulder kinematics because of their anatomic attachments. [178] (10.1016/j.arthro.2009.12.031)
• [L4] Adolescent multidirectional shoulder instability refractory to non-surgical management appears to have long-term outcomes after surgical intervention that are comparable to adolescent patients with unidirectional instability. [179] (10.1177/2325967121s00021)
• [L3] The modified position of the scapula was maintained during the entire range of motion, suggesting a shoulder-stabilizing kinematic effect in addition to the bony, sling and bumper effects. [180] (10.1016/j.jse.2024.02.022)
• [L5] During the simulated acceleration phase of the throwing motion, anterior glenohumeral translation significantly increased as shoulder abduction decreased. [182] (10.1016/j.jse.2017.12.029)
• [L5] Time-zero biomechanical shoulder instability studies are valuable but limited because they do not replicate clinical dynamics, and the observed results do not confirm that the surgical approach would provide sufficient long-term noncontractile shoulder stability to withstand repetitive soft-tissue loading in a dynamic, clinical situation. [183] (10.1016/j.arthro.2022.04.006)
• [L4] Arthroscopic treatment of posterior shoulder instability is an effective means to improve symptoms associated with recurrent posterior subluxation of the shoulder. [184] (10.1177/0363546505278301)
• [L4] Results in this series demonstrate the efficacy and durability of a modified capsular shift procedure for the treatment of atraumatic anterior-inferior shoulder instability. [186] (10.1177/0363546504272685)
• [L5] Kinematic analysis of patients with rotator cuff tears shows unexpected inferior, rather than superior, translation of the humeral head; this paradox challenges conventional thought, but limitations addressed by the authors temper the results and leave the question open for future study. [189] (10.1016/j.arthro.2015.12.031)
• [L3] Further research is needed to determine the biomechanical and clinical context in which a more superior CP position is associated with anteroinferior glenohumeral instability. [190] (10.1016/j.jseint.2026.101785)
• [L4] Arthroscopic stabilization of posterior shoulder instability resulted in good outcomes with high patient satisfaction and low rates of recurrent instability, revisions, and residual pain. [192] (10.1016/j.jse.2024.04.006)
• [L5] There are discrepancies in the definition and classification of multidirectional instability, which can make diagnosis and treatment selection challenging. [193] (10.1016/j.jht.2017.03.005)
• [L4] Pelvic position affects shoulder range of motion. [194] (10.1186/s12891-025-08280-0)
• [L5] Both muscles had increased extension and internal rotation moment arms at higher degrees of elevation compared with the native shoulders. [195] (10.1016/j.jse.2023.10.011)
• [L5] Multiple anterior shoulder dislocations lead to abnormal translational kinematics and result in increased superior translation of the humerus. [196] (10.1007/s00167-022-07257-z)
• [L5] Scapular and clavicular kinematics were affected in AC separation models. [197] (10.1016/j.jse.2013.01.004)
• [L4] Current evidence supports the safety and efficacy of both the Latarjet and FBB procedures for anterior shoulder stabilization in the presence of glenoid bone loss. [198] (10.1177/0363546520925833)
• [L4] The proposed procedure demonstrated effectiveness and safety, being a viable option for treating anterior shoulder instability with glenoid bone loss of less than 20% and especially beneficial for athletes. [199] (10.1016/j.jseint.2024.06.016)
• [L5] Conventional radiography remains the initial imaging study for evaluating patients with persistent shoulder pain and instability, while magnetic resonance arthrography has been firmly established as the imaging modality of choice for demonstrating specific soft tissue abnormalities associated with glenohumeral instability. [201] (10.1177/03635465000280032501)
• [L3] Nonoperative treatment of shoulder instability has substantial societal costs. [205] (10.1177/1758573218773543)
• [L4] The Latarjet procedure for anterior shoulder instability results in an overall complication rate of 16.1% and a reoperation rate of 2.6%, though serious complications at short-term follow-up appear rare. [206] (10.1177/03635465211042314)
• [L4] The proposed classification system is a helpful guide to the degree of glenoid bone loss when embarking on revision shoulder arthroplasty. [208] (10.1302/0301-620x.98b3.36664)
• [L3] For experienced shoulder surgeons, the Snyder classification is a reliable system for identifying SLAP lesions. [209] (10.1177/0363546510392332)
• [L2] The FEDS system has content validity and is highly reliable for classifying glenohumeral instability. [210] (10.1016/j.jse.2010.10.027)
• [L3] Objective and subjective scoring systems correlate significantly with the clinical condition of patients with recurrent shoulder instability and associated bony defects. [212] (10.1177/0363546515626541)
• [L4] Recent studies continue to demonstrate a role for nonoperative treatment in the successful long-term management of anterior glenohumeral instability. [214] (10.1007/s12178-017-9432-5)
• [L3] Female patients undergoing the Latarjet procedure for recurrent shoulder instability showed similar 90-day complication and 2-year secondary surgery rates to a matched cohort of male patients. [215] (10.1016/j.arthro.2024.02.043)
• [L4] The formation of clusters based on glenoid morphology indicates that patterns exist in the types of glenoid defects, highlighting a need to further investigate a three-dimensional classification system and potentially new standardized revision implant component designs. [217] (10.1016/j.jse.2026.04.002)
• [L5] Arthroscopic repair for posterior shoulder instability yields favorable mid-term outcomes, with significant improvements in functional scores and a low recurrence rate at a mean follow-up of 10.6 years. [219] (10.1016/j.arthro.2025.07.040)
• [L4] This combination has long-term outcomes in terms of the recurrence rate and does not significantly influence the range of motion of the shoulder. [221] (10.1007/s00167-018-5261-3)
• [L4] NHL team physicians strongly favor nonoperative management in-season for initial posterior instability events of the shoulder. [224] (10.1177/23259671261440208)
• [L1] Despite the wide array of available PROMs for assessing shoulder instability surgery outcomes, the availability of clinically significant outcome thresholds such as MCID and PASS remains relatively limited. [226] (10.1016/j.arthro.2024.07.039)
• [L4] [227] (10.1177/17585732261439731)
• [L1] This study supports the need for standardized outcome reporting after arthroscopic anterior shoulder instability surgery in adolescents. [228] (10.1016/j.arthro.2017.10.041)
• [L4] Arthroscopic capsulolabral repair for posterior shoulder instability was a durable treatment option that improved long-term shoulder pain and function and facilitated return to sport in the majority of patients at a mean follow-up of 15.4 years, although a notable proportion of patients met various criteria for failure. [229] (10.1177/03635465231162271)
• [Case_report] Patients with a history of shoulder instability or replacement are at risk for shoulder dislocation during common elbow and hand procedures. [230] (10.1016/j.jse.2020.04.012)
• [L1] There was no evidence regarding the effectiveness of surgical management for post-traumatic chronic shoulder instability. [232] (10.1136/bjsports-2017-098539)
• [L5] Magnetic resonance arthrography is regarded as the gold-standard imaging modality for shoulder instability. [234] (10.1016/j.mric.2019.12.005)
• [L3] Surgical shoulder stabilization in an athlete after a first episode of instability is not indicated in all patients. [235] (10.1016/j.arthro.2017.04.088)
• [L3] [238] (10.1007/s00167-020-06388-5)
• [L4] The recurrence of anterior shoulder instability can be as high as 86.7% in high-risk patients who are treated nonoperatively after their first incident of instability. [239] (10.5435/jaaosglobal-d-19-00168)
• [L1] Capsular injury is commonly seen in magnetic resonance imaging of patients with anterior shoulder instability. [240] (10.1016/j.xrrt.2024.08.004)
• [L4] This large systematic review demonstrates the overall complication rates in modern shoulder stabilization surgery. [241] (10.1177/0363546518810711)
• [L4] By contrast, the presence of a posterior glenoid fracture (bony Bankart lesion) did not represent a contraindication to arthroscopic shoulder stabilization. [242] (10.1177/03635465251403499)
• [L4] Recurrent instability requiring capsular reconstruction seems to be more prevalent in patients with a previous history of shoulder dislocation. [243] (10.1016/j.jse.2009.07.062)
• [L4] [245] (10.1177/17585732231154889)
• [Paper] Advanced imaging modalities are essential for identifying associated lesions, and bony reconstruction procedures should be considered for patients with significant glenoid bone loss or recurrent instability after soft tissue reconstruction. [246] (10.1016/j.csm.2014.06.006)
• [L2] Early arthroscopic stabilization by anterior capsule-labrum reinsertion after initial anterior shoulder dislocation is associated with a low 10-year recurrence rate of 35% compared to non-operative management. [248] (10.1016/j.otsr.2015.09.029)
• [L4] [251] (10.1016/j.jse.2019.12.012)
• [L3] Magnetic resonance arthrography was an accurate method to assess accompanying lesions in first-time and recurrent anterior dislocation of the shoulder. [252] (10.1177/0363546510371607)
• [L5] [253] (10.1177/1758573218815002)
• [L4] [254] (10.1016/j.jse.2005.11.011)
• [L1] There is insufficient evidence from randomised trials comparing arthroscopic with open surgery for treating anterior shoulder instability. [255] (10.1002/14651858.cd005077.pub2)
• [L3] This useful MRI measurement may help identify patients at risk for primary or recurrent anterior glenohumeral instability events and may therefore help with guiding treatment and prevention. [256] (10.1177/2325967120986139)
• [L3] Despite the advantages of MRI in the detection of soft tissue damages in recurrent anterior shoulder instability CT imaging proved to be more important for glenoid defects. [257] (10.1007/s00402-012-1656-7)
• [L1] Early operative stabilization of Bankart lesions in young patients offers a significant reduction in the risk of recurrent instability compared to non-operative management. [258] (10.1111/j.1758-5740.2010.00083.x)
• [L3] Preoperative risk factors included history of bilateral shoulder instability and atraumatic mechanism of dislocation. [260] (10.1177/2325967120s00378)
• [L3] In a US epidemiologic population of patients <40 years old, the rate of recurrent anterior shoulder instability was roughly one-third after initial physician consultation. [262] (10.1177/0363546519886861)
• [L4] CT and MRI (2D or 3D) accurately measure glenoid bone loss in anterior shoulder instability, but radiographs do not. [263] (10.2214/ajr.18.20504)
• [L4] The iliac posterior shoulder bone-block is effective in managing instances of involuntary posterior shoulder instability, showing satisfactory results in terms of non-recurrence, pain relief, and function recovery. [264] (10.1016/j.otsr.2008.09.008)
• [L1] Arthroscopic lavage reduced the recurrence rate and produced a better functional outcome at 1-year follow-up than non-operative treatment in young individuals with traumatic primary anterior shoulder dislocation. [265] (10.1007/s001670050146)
• [L4] [267] (10.1016/j.jse.2024.09.022)
• [L4] [269] (10.1007/s12178-011-9092-9)
• [L5] MR-arthrography is identified as the main tool in diagnosing shoulder instability injuries. [271] (10.21037/qims.2017.08.05)
• [L5] [275] (10.5435/jaaos-d-19-00535)
• [L4] Magnetic resonance angiography has a high sensitivity when used to identify associated injuries in shoulder dislocation, although in 8 patients (13 %) arthroscopy identified an additional injury. [283] (10.1007/s00256-014-2080-6)
• [L2] Overall, 3D MRI is a validated and reliable alternative to 3D CT for preoperative evaluation of static glenohumeral bone loss and dynamic morphological variables in shoulder instability, allowing clinicians to choose the modality that best fits their practice. [287] (10.1177/23259671251343325)
• [L3] Overall, 3D MRI is a validated and reliable alternative to 3D CT for preoperative evaluation of static glenohumeral bone loss and dynamic morphological variables in shoulder instability, allowing clinicians to choose the modality that best fits their practice. [288] (10.1177/2325967125s00129)
• [L4] In the future, we expect CT to be superseded by MRI in anterior shoulder instability. [289] (10.1016/j.jseint.2025.101440)
• [L5] In patients with suspected posterior glenohumeral instability, imaging of the affected shoulder can show abnormalities of the bone, labrum, and joint capsule. [290] (10.2214/ajr.07.3849)
• [L3] Patients who undergo MRI greater than 6 months from the time of primary shoulder dislocation demonstrate a greater incidence and severity of intra‐articular pathology including SLAP tears, posterior labral tears and anterior glenoid cartilage damage. [292] (10.1177/2325967117s00360)
• [L4] [293] (10.1016/j.jse.2017.01.027)
• [L1] [295] (10.2106/jbjs.8908.ebo1)
• [L5] Even without posterior instability complaints or findings, in patients with posterior shoulder pain during daily activities or sports, posterior labral tears should be considered even when MRI or MRA findings are ambiguous. [297] (10.1016/j.arthro.2023.07.004)
• [L4] [298] (10.1016/j.jisako.2025.100765)
• [L4] Radiography can be used for screening patients for significant glenoid bone loss. [301] (10.1186/s12891-015-0607-1)
• [L3] The superior-capsular elongation as well as its diagnostic criteria of measurements by MR arthrography revealed in the present study could serve as references for diagnosing atraumatic posteroinferior shoulder instability and offer insight into the spectrum of imaging findings corresponding to the pathologies encountered at clinical presentation. [303] (10.3109/02841850903524421)
• [L3] Routine MRI has similar diagnostic value to MR arthrogram for measuring labral tear extent up to approximately 2 weeks postacute shoulder dislocation, after which it significantly loses accuracy and precision. [305] (10.1177/2325967124s00075)
• [L3] ZTE MRI demonstrated high reproducibility for the evaluation of glenoid bone defect in shoulders with anterior instability. [307] (10.1016/j.jseint.2024.03.003)
• [L4] Patients with multidirectional instability demonstrated quantifiable dynamic instability on cine MRI with significantly greater humeral head deviation and faster deviation velocity than healthy controls. [309] (10.1016/j.jseint.2025.101419)
• [L4] Additionally, MRI is a valid imaging tool to diagnose and measure osseous lesions of the shoulder. [310] (10.1007/s00247-018-4318-2)
• [L4] Posterior HAGL lesions identified on radiographic imaging are not clinically significant unless the patient has symptoms and a history specific for posterior instability. [311] (10.1016/j.arthro.2007.03.020)
• [L4] Arthrotomography of the glenoid labrum is a helpful adjunct in substantiating the diagnosis of shoulder instability and in planning the choice of surgical reconstruction. [312] (10.2106/00004623-198264040-00005)
• [L3] Bone defects seen in preoperative plain radiographs are less important and more accurate imaging is needed to reveal their true role for recurrence of instability. [313] (10.1007/s00167-010-1105-5)
• [L4] Simultaneous bilateral posterior shoulder dislocation is a rare entity that requires careful clinical and radiological evaluation, often necessitating CT scans for diagnosis. [314] (10.1007/s00167-006-0066-1)
• [L4] In our series 9 shoulders (45%) remained completely stable at 3.8 years. [315] (10.1016/j.arthro.2011.07.002)
• [L4] The number of episodes of dislocation before surgery and the delayed surgical intervention did not increase the recurrent anterior shoulder instability rates postoperatively. [317] (10.1016/j.jseint.2022.12.003)
• [L3] In our cohort of young patients undergoing arthroscopic surgery for posterior shoulder instability, we detected no significant difference in reoperation rate and recurrence of symptoms between athletes who underwent objective return to sport testing and those who were released to sport on a time-based protocol. [318] (10.1177/2325967121s00549)
• [L3] In our cohort of young patients undergoing arthroscopic surgery for posterior shoulder instability, we detected no significant difference in reoperation rate and recurrence of symptoms between athletes who underwent objective return to sport testing and those who were released to sport on a time‐based protocol. [319] (10.1177/2325967121s00593)
• [L3] Patients treated conservatively for anterior shoulder instability were far more likely to achieve a successful outcome defined as completing a subsequent season in their same sport compared to surgical patients. [320] (10.1177/2325967117s00284)
• [L4] Shoulder arthroplasty in the setting of prior anterior instability results in improved subjective and functional outcome scores that are comparable to patients without a history of instability. [321] (10.1016/j.jseint.2022.08.012)

See Also

• Rotator Cuff
• Latarjet Procedure
• Shoulder Arthroplasty
• Thoracic Outlet Syndrome
• Frozen Shoulder
• Total shoulder arthroplasty
• Fractures

References

[1] Assessment and diagnosis of non-traumatic shoulder instability: A scoping review. Shoulder & Elbow. 2025. DOI: 10.1177/17585732251320070

[2] Descriptive Epidemiology of the MOON Shoulder Instability Cohort. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518755752

[3] Orthopaedic Knowledge Update Sports Medicine 6. Research Studies and Registries in Sports Medicine > Multicenter and Registry-­Based Research in Sports Medicine > Shoulder Research.

[4] Aaos Comprehensive Orthopaedic Review 3. The Unstable Shoulder > V. Multidirectional Instability.

[5] (ii) The classification of shoulder instability: new light through old windows!. Current Orthopaedics. 2004. DOI: 10.1016/j.cuor.2004.04.002

[7] Non-operative Management of Posterior Shoulder Instability: An Assessment of Survival and Predictors for Conversion to Surgery at 1 to 13 Years After Diagnosis. Orthopaedic Journal of Sports Medicine. 2018. DOI: 10.1177/2325967118s00098

[8] Nonoperative management of anterior shoulder instability can result in high rates of recurrent instability and pain at long-term follow-up. Journal of Shoulder and Elbow Surgery. 2022. DOI: 10.1016/j.jse.2021.07.016

[9] High Variability of the Definition of Recurrent Glenohumeral Instability: An Analysis of the Current Literature by a Systematic Review. Arthroscopy, Sports Medicine, and Rehabilitation. 2021. DOI: 10.1016/j.asmr.2021.02.002

[10] Proper Evaluation of Bone Loss Determines Shoulder Instability Indications and Outcomes. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2021. DOI: 10.1016/j.arthro.2021.01.004

[11] Posterior shoulder instability: Prospective non-randomised comparison of operative and non-operative treatment in 51 patients. Orthopaedics & Traumatology: Surgery & Research. 2017. DOI: 10.1016/j.otsr.2017.08.004

[12] The Continuous Fragility Index of Statistically Significant Findings in Randomized Controlled Trials That Compare Interventions for Anterior Shoulder Instability. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465231202522

[13] Rockwood And Matsen S The Shoulder. Fractures, Dislocations, and Acquired Problems of the Shoulder in Children > CONCLUSIONS.

[14] Aaos Comprehensive Orthopaedic Review 3. The Unstable Shoulder > IV. Posterior Instability.

[15] Arthroscopic Treatment of Posterior Shoulder Instability: A Systematic Review. Arthroscopy. 2014. DOI: 10.1016/j.arthro.2014.11.009

[16] Rockwood And Matsen S The Shoulder. Fractures, Dislocations, and Acquired Problems of the Shoulder in Children > Operative Management of Posterior Instability.

[17] Multiple Instability Events at Initial Presentation Are the Major Predictor of Failure of Nonoperative Treatment for Anterior Shoulder Instability. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2021. DOI: 10.1016/j.arthro.2021.03.047

[18] Shoulder Instability in Women Compared with Men. JBJS Reviews. 2019. DOI: 10.2106/jbjs.rvw.19.00007

[19] International survey and surgeon’s preferences in diagnostic work-up towards treatment of anterior shoulder instability. Archives of Orthopaedic and Trauma Surgery. 2016. DOI: 10.1007/s00402-016-2443-7

[20] Consensus Statement on Shoulder Instability. Arthroscopy. 2009. DOI: 10.1016/j.arthro.2009.06.022

[21] Biomechanics of posterior shoulder instability - current knowledge and literature review. World Journal of Orthopedics. 2018. DOI: 10.5312/wjo.v9.i11.245

[22] Failure of Operative Treatment for Glenohumeral Instability: Etiology and Management. Arthroscopy. 2011. DOI: 10.1016/j.arthro.2010.11.057

[23] Comprehensive Review of Shoulder Instability Includes Diagnosis, Nonoperative Management, Bankart, Latarjet, Remplissage, Glenoid Bone‐Grafting, Revision Surgery, Rehabilitation and Return to Play, and Clinical Follow‐Up. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2021.11.052

[24] No difference in outcomes for posterior shoulder instability surgery in patients with a normal vs. pathological radiologist reported magnetic resonance arthrogram study. JSES Reviews, Reports, and Techniques. 2026. DOI: 10.1016/j.xrrt.2026.100675

[25] Substantial variability in what is considered important in the radiological report for anterior shoulder instability: a Delphi study with Dutch musculoskeletal radiologists and orthopedic surgeons. JSES International. 2024. DOI: 10.1016/j.jseint.2024.03.012

[27] Rockwood And Matsen S The Shoulder. Arthroscopic Management of Prearthritic and Arthritic Conditions of the Shoulder and the Postarthroplasty Shoulder > Instability.

[28] Rockwood And Matsen S The Shoulder. Fractures, Dislocations, and Acquired Problems of the Shoulder in Children > ARTHROSCOPIC MANAGEMENT OF POSTTRAUMATIC ANTERIOR INSTABILITY.

[29] Predicting Failure After Primary Arthroscopic Bankart Repair: Analysis of a Statistical Model Using Anatomic Risk Factors. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2020. DOI: 10.1016/j.arthro.2019.11.109

[30] Translation and validation of the French version of the Western Ontario Shoulder Instability Index (WOSI): WOSI-Fr. Orthopaedics & Traumatology: Surgery & Research. 2017. DOI: 10.1016/j.otsr.2016.10.024

[31] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Shoulder Instability, Rotator Cuff Disorders, Muscular Ruptures, Adhesive Capsulitis, Calcific Tendinitis > Shoulder Instability > Anterior Instability.

[32] 360° Around Shoulder Instability. 2020.

[33] Recurrent Posterior Shoulder Instability. Journal of the American Academy of Orthopaedic Surgeons. 2006. DOI: 10.5435/00124635-200608000-00004

[36] Children and adolescents with all forms of shoulder instability demonstrate differences in their movement and muscle activity patterns when compared to age- and sex-matched controls. Journal of Shoulder and Elbow Surgery. 2024. DOI: 10.1016/j.jse.2024.01.043

[37] Critical Findings on Magnetic Resonance Arthrograms in Posterior Shoulder Instability Compared With an Age-Matched Controlled Cohort. The American Journal of Sports Medicine. 2016. DOI: 10.1177/0363546516660076

[38] A predictive model of shoulder instability after a first-time anterior shoulder dislocation. Journal of Shoulder and Elbow Surgery. 2011. DOI: 10.1016/j.jse.2010.10.037

[39] Free Bone Block Procedures for Glenoid Reconstruction in Anterior Shoulder Instability. Journal of the American Academy of Orthopaedic Surgeons. 2023. DOI: 10.5435/jaaos-d-22-00837

[40] Acute Traumatic Posterior Shoulder Dislocation. Journal of the American Academy of Orthopaedic Surgeons. 2014. DOI: 10.5435/jaaos-22-03-145

[41] Accuracy and Reliability of Imaging Modalities for the Diagnosis and Quantification of Hill‐Sachs Lesions: A Systematic Review. Arthroscopy. 2020. DOI: 10.1016/j.arthro.2020.08.005

[42] Minor or occult shoulder instability: an intra‐articular pathology presenting with extra‐articular subacromial impingement symptoms. Knee Surgery, Sports Traumatology, Arthroscopy. 2011. DOI: 10.1007/s00167-011-1552-7

[43] The clinical physiotherapy assessment of non-traumatic shoulder instability. Shoulder & Elbow. 2014. DOI: 10.1177/1758573214548934

[44] Rockwood And Matsen S The Shoulder. Developmental Anatomy of the Shoulder and Anatomy of the Glenohumeral Joint > SENIOR EDITOR COMMENTARY.

[45] Shoulder Instability: Surgical Versus Nonsurgical Treatment. Arthroscopy. 2007. DOI: 10.1016/j.arthro.2006.11.026

[46] Predictors for Surgery in Shoulder Instability. Orthopaedic Journal of Sports Medicine. 2015. DOI: 10.1177/2325967115607434

[49] Defining clinical significance following primary stabilization of posterior shoulder instability. JSES International. 2025. DOI: 10.1016/j.jseint.2025.08.006

[50] The management of secondary frozen shoulder after anterior shoulder dislocation – The results of manipulation under anaesthesia and injection. Journal of Orthopaedics. 2016. DOI: 10.1016/j.jor.2015.01.030

[51] Shoulder Instability: Management and Rehabilitation. Journal of Orthopaedic & Sports Physical Therapy. 2002. DOI: 10.2519/jospt.2002.32.10.497

[52] Rockwood And Matsen S The Shoulder. Fractures, Dislocations, and Acquired Problems of the Shoulder in Children > Multidirectional Instability.

[53] Classifications And Scores Of The Shoulder. 7.9 Classification of shoulder instability according to Gerber et al. [44, 45, 118]*.

[54] Current Approaches to Arthroscopic Management of Anterior Shoulder Instability. JBJS Reviews. 2026. DOI: 10.2106/jbjs.rvw.26.00033

[55] Long-term Results After Arthroscopic Shoulder Stabilization Using Suture Anchors. The American Journal of Sports Medicine. 2011. DOI: 10.1177/0363546511415657

[56] Pre‐shaped Allograft for Glenoid Reconstruction in Anterior Shoulder Instability. Arthroscopy Techniques. 2018. DOI: 10.1016/j.eats.2017.10.007

[57] An assessment of quality of randomized controlled trials in shoulder instability surgery using a modification of the clear CLEAR-NPT score. Shoulder & Elbow. 2018. DOI: 10.1177/1758573218754370

[58] Diagnosis and treatment of posterior shoulder instability based on the ABC classification. EFORT Open Reviews. 2024. DOI: 10.1530/eor-24-0025

[61] Primary Arthroscopic Stabilization for a First-Time Anterior Dislocation of the Shoulder. Journal of Bone and Joint Surgery. 2019. DOI: 10.2106/jbjs.19.00858

[64] Outcomes of total shoulder arthroplasty in patients with prior anterior shoulder instability: minimum 5-year follow-up. Journal of Shoulder and Elbow Surgery. 2024. DOI: 10.1016/j.jse.2023.07.005

[65] Long-Term Prognosis Of First Time Anterior Shoulder Dislocation In The Young: 229 Shoulders Prospectively Followed For 25 Years. Journal of Shoulder and Elbow Surgery. 2007. DOI: 10.1016/j.jse.2007.02.100

[68] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Shoulder Instability, Rotator Cuff Disorders, Muscular Ruptures, Adhesive Capsulitis, Calcific Tendinitis > Shoulder Instability > Posterior Instability.

[69] Rockwood And Matsen S The Shoulder. Developmental Anatomy of the Shoulder and Anatomy of the Glenohumeral Joint > Instability.

[70] Latarjet Procedure for Anterior Shoulder Instability: A 24-Year Follow Up Study. Journal of Shoulder and Elbow Surgery. 2021. DOI: 10.1016/j.jse.2021.03.097

[71] Latarjet procedure for anterior shoulder instability: a 24-year follow-up study. Archives of Orthopaedic and Trauma Surgery. 2020. DOI: 10.1007/s00402-020-03426-2

[73] Patients Aged >50 Years With Anterior Shoulder Instability Have a Decreased Risk of Recurrent Dislocation After Operative Treatment Compared With Non‐Operative Treatment. Arthroscopy, Sports Medicine, and Rehabilitation. 2023. DOI: 10.1016/j.asmr.2023.03.014

[74] Long-term outcomes of the Latarjet procedure in a North American population. JSES International. 2025. DOI: 10.1016/j.jseint.2025.04.033

[75] Osteoarthritis Following Shoulder Instability. Clinics in Sports Medicine. 2005. DOI: 10.1016/j.csm.2004.08.010

[76] Variability in Outcome Reporting for Operatively Managed Anterior Glenohumeral Instability: A Systematic Review. Arthroscopy. 2016. DOI: 10.1016/j.arthro.2016.07.027

[77] Posterior Shoulder Instability, Part I—Diagnosis, Nonoperative Management, and Labral Repair for Posterior Shoulder Instability—An International Expert Delphi Consensus Statement. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.04.035

[78] Classifications And Scores Of The Shoulder. 7.10 Classification of shoulder instability according to Bayley et al. [5, 6]*.

[79] Editorial Commentary: Glenoid Bone Reconstruction for Recurrent Shoulder Instability—Risk or Benefit?. Arthroscopy. 2016. DOI: 10.1016/j.arthro.2016.06.032

[80] Long-Term Functional, Sports- and Work-Related Outcomes After Arthroscopic Capsulolabral Revision Repair for Recurrent Anterior Shoulder Instability: A Minimum 20-Year Follow-up. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/23259671251376528

[81] Natural History of First-Time Anterior Shoulder Dislocation in Patients Older Than 50 Years: A Study of 179 Patients With a Mean Follow-up of 11 Years. Orthopaedic Journal of Sports Medicine. 2022. DOI: 10.1177/23259671221129301

[83] Risk of arthropathy after the Bristow-Latarjet repair: a radiologic and clinical thirty-three to thirty-five years of follow-up of thirty-one shoulders. Journal of Shoulder and Elbow Surgery. 2015. DOI: 10.1016/j.jse.2014.09.021

[87] Does Labral Reconstruction Prevent Osteoarthritis After Posterior Shoulder Instability: A Population-Based Study. Orthopaedic Journal of Sports Medicine. 2018. DOI: 10.1177/2325967118s00154

[88] Rockwood And Matsen S The Shoulder. Shoulder and Elbow Specialty Clinic Workers’ Survey > ANATOMY.

[89] Effects of glenoid inclination and acromion index on humeral head translation and glenoid articular cartilage strain. Journal of Shoulder and Elbow Surgery. 2017. DOI: 10.1016/j.jse.2016.05.031

[90] A Lange Medical Book Current Diagnosis Treatment In Orthopedics Fifth Edition. 2Musculoskeletal Trauma Surgery > SHOULDER AND ARM INJURIES.

[92] Aaos Comprehensive Orthopaedic Review 3. Anatomy of the Shoulder, Arm, and Elbow > I. Shoulder.

[96] Rockwood And Matsen S The Shoulder. Fractures, Dislocations, and Acquired Problems of the Shoulder in Children > FRACTURES OF THE PROXIMAL HUMERUS.

[97] Rockwood And Matsen S The Shoulder. Developmental Anatomy of the Shoulder and Anatomy of the Glenohumeral Joint > Development of Individual Regions.

[99] Campbell S Operative Orthopaedics 4 Volume Set. RECONSTRUCTIVE PROCEDURES OF THE SHOULDER AND ELBOW IN ADULTS > ANATOMY AND BIOMECHANICS.

[100] Campbell S Operative Orthopaedics 4 Volume Set. ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION WITH BONE-PATELLAR TENDON-BONE GRAFT > SHOULDER INJURIES > ANATOMY AND BIOMECHANICS.

[102] Miller S Review Of Orthopaedics. Genetics of musculoskeletal conditions and abnormalities are summarized in Table 1.27 > UPPER EXTREMITY > SHOULDER.

[104] Changes in Scapular Function, Shoulder Strength, and Range of Motion Occur After Latarjet Procedure. Arthroscopy, Sports Medicine, and Rehabilitation. 2023. DOI: 10.1016/j.asmr.2023.100804

[105] Arthroscopic Findings After Traumatic Shoulder Instability in Patients Older Than 35 Years. Orthopaedic Journal of Sports Medicine. 2015. DOI: 10.1177/2325967115584318

[106] Rockwood And Matsen S The Shoulder. Developmental Anatomy of the Shoulder and Anatomy of the Glenohumeral Joint > Shoulder Capsule.

[110] Unperceived First-Time Anterior Shoulder Subluxation: The Role of MRI in Detection and Characterization of Pathoanatomy. Orthopaedic Journal of Sports Medicine. 2026. DOI: 10.1177/23259671251414851

[111] Traumatic 270° and 360° labral tears of shoulder – Injury patterns, surgical technique, and mid-term outcomes. Shoulder & Elbow. 2025. DOI: 10.1177/17585732251316476

[112] Evidence-Based Review of Clinical Diagnostic Tests and Predictive Clinical Tests That Evaluate Response to Conservative Rehabilitation for Posterior Glenohumeral Instability: A Systematic Review. Sports Health: A Multidisciplinary Approach. 2018. DOI: 10.1177/1941738117752306

[113] A new classification system for shoulder instability. British Journal of Sports Medicine. 2010. DOI: 10.1136/bjsm.2009.071183

[116] Effect of Shortening Deformity of the Clavicle on Scapular Kinematics. The American Journal of Sports Medicine. 2010. DOI: 10.1177/0363546509355143

[120] Early Rehabilitation After a Modified Inferior Capsular Shift Procedure for Multidirectional Instability of the Shoulder. 1998.

[125] Recurrence and return to play after shoulder instability events in young and adolescent athletes: a systematic review and meta-analysis. British Journal of Sports Medicine. 2016. DOI: 10.1136/bjsports-2016-096895

[127] Posterior Humeral Avulsion of the Glenohumeral Ligament: A Clinical Review of 9 Cases. Arthroscopy. 2007. DOI: 10.1016/j.arthro.2007.02.006

[129] Rockwood And Matsen S The Shoulder. Arthroscopic Management of Prearthritic and Arthritic Conditions of the Shoulder and the Postarthroplasty Shoulder > THROWING SHOULDER CONDITIONS.

[131] Intraobserver and interobserver agreement of International Classification of Diseases, Ninth Revision codes in classifying shoulder instability. Journal of Shoulder and Elbow Surgery. 2009. DOI: 10.1016/j.jse.2008.10.005

[132] Microinstability characterised by small and easily overlooked anterior labral or Hill–Sachs lesions can be managed with arthroscopic anterior labral repair. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-06941-4

[135] Arthroscopic Repair of Humeral Avulsion of the Glenohumeral Ligament for Anterior Shoulder Instability. Arthroscopy Techniques. 2021. DOI: 10.1016/j.eats.2020.10.053

[137] Understanding the Glenoid Avulsion of the Glenohumeral Ligaments as a Cause of Shoulder Instability: Surgical and Postsurgical Management. Arthroscopy Techniques. 2019. DOI: 10.1016/j.eats.2019.06.001

[140] Recurrent anterior shoulder instability: Review of the literature and current concepts. World Journal of Clinical Cases. 2014. DOI: 10.12998/wjcc.v2.i11.676

[143] Atypical Shoulder Instability Patterns in Adolescents Following Traumatic Anterior Shoulder Dislocation. The American Journal of Sports Medicine. 2023. DOI: 10.1177/03635465231171129

[147] Biomechanical comparison of the modified Bristow procedure with and without capsular repair. Knee Surgery, Sports Traumatology, Arthroscopy. 2015. DOI: 10.1007/s00167-015-3915-y

[148] Outcomes of capsulolabral reconstruction for posterior shoulder instability. Orthopaedics & Traumatology: Surgery & Research. 2017. DOI: 10.1016/j.otsr.2017.08.002

[149] The Effect of Glenohumeral Internal Rotation Deficit Due to Posterior Capsular Contracture on Passive Glenohumeral Joint Motion. The American Journal of Sports Medicine. 2012. DOI: 10.1177/0363546512462012

[150] The Effect of Posterosuperior Rotator Cuff Tears and Biceps Loading on Glenohumeral Translation. Arthroscopy. 2010. DOI: 10.1016/j.arthro.2009.09.007

[151] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Shoulder Anatomy and Biomechanics, Clinical Evaluation, Imaging > Clinical Evaluation > Imaging.

[152] Editorial Commentary: Recurrent Anterior Shoulder Instability With Glenoid Bone Loss Requires Restoring the Bone. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2021.09.002

[153] Rockwood And Matsen S The Shoulder. Fractures, Dislocations, and Acquired Problems of the Shoulder in Children > DIAGNOSIS AND DIAGNOSTIC ARTHROSCOPY IN SHOULDER INSTABILITY.

[154] The Effect of Anterosuperior Rotator Cuff Tears on Glenohumeral Translation. Arthroscopy. 2008. DOI: 10.1016/j.arthro.2008.10.005

[155] Outcomes of the Latarjet procedure with minimum 5- and 10-year follow-up: A systematic review. Shoulder & Elbow. 2020. DOI: 10.1177/1758573220945318

[156] Orthopaedic Knowledge Update Sports Medicine 6. Shoulder Instability > Anterior Instability > Management.

[157] Aaos Comprehensive Orthopaedic Review 3. Imaging of the Shoulder and Elbow > I. Shoulder.

[158] Miller S Review Of Orthopaedics. SHOULDER INSTABILITY > History and physical examination.

[162] Rockwood And Matsen S The Shoulder. Fractures, Dislocations, and Acquired Problems of the Shoulder in Children > Clinical Findings.

[163] Effects of short malunion of the clavicle on in vivo scapular kinematics. Journal of Shoulder and Elbow Surgery. 2017. DOI: 10.1016/j.jse.2017.03.013

[165] Suture Capsulorrhaphy Versus Capsulolabral Advancement for Shoulder Instability. Arthroscopy. 2012. DOI: 10.1016/j.arthro.2012.04.140

[166] Arthroscopic Repair for Posterior Shoulder Instability Is Associated With Favorable Outcomes and High Return to Sport or Work: A Systematic Review and Meta‐Analysis. Arthroscopy, Sports Medicine, and Rehabilitation. 2024. DOI: 10.1016/j.asmr.2024.101032

[167] Lesion prevalence and patient outcome comparison between primary and recurrent anterior shoulder instability. Journal of Shoulder and Elbow Surgery. 2023. DOI: 10.1016/j.jse.2023.05.029

[168] Arthroscopic versus Open Shoulder Stabilization for Recurrent Anterior Instability. The American Journal of Sports Medicine. 2006. DOI: 10.1177/0363546506288239

[170] ABC classification of posterior shoulder instability. Obere Extremität. 2017. DOI: 10.1007/s11678-017-0404-6

[172] Glenohumeral decentering in rotator cuff deficiency: relationship to rotator cuff muscle, scapula morphology, and shoulder function. Journal of Shoulder and Elbow Surgery. 2026. DOI: 10.1016/j.jse.2025.03.038

[174] Open Repairs for the Treatment of Anterior Shoulder Instability. The American Journal of Sports Medicine. 2003. DOI: 10.1177/03635465030310011001

[175] Movement control in patients with shoulder instability: a comparison between patients after open surgery and nonoperated patients. Journal of Shoulder and Elbow Surgery. 2014. DOI: 10.1016/j.jse.2013.09.021

[176] Partial-thickness tears involving the rotator cable lead to abnormal glenohumeral kinematics. Journal of Shoulder and Elbow Surgery. 2017. DOI: 10.1016/j.jse.2016.12.063

[178] A Biomechanical Analysis of the Native Coracoclavicular Ligaments and Their Influence on a New Reconstruction Using a Coracoid Tunnel and Free Tendon Graft. Arthroscopy. 2010. DOI: 10.1016/j.arthro.2009.12.031

[179] MEAN 6 YEAR CLINICAL OUTCOMES, SURVIVORSHIP, AND RETURN TO SPORTS AFTER ARTHROSCOPIC CAPSULAR REPAIR WITH SUTURE ANCHORS FOR ADOLESCENT MULTIDIRECTIONAL SHOULDER INSTABILITY. Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/2325967121s00021

[180] Kinematic stabilization after the Latarjet procedure: beyond the triple blocking effect. Journal of Shoulder and Elbow Surgery. 2024. DOI: 10.1016/j.jse.2024.02.022

[182] Lower shoulder abduction during throwing motion may cause forceful internal impingement and decreased anterior stability. Journal of Shoulder and Elbow Surgery. 2018. DOI: 10.1016/j.jse.2017.12.029

[183] Editorial Commentary : Time‐Zero Biomechanical Shoulder Instability Studies Are Valuable But Limited Because They Do Not Replicate Clinical Dynamics. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2022.04.006

[184] Arthroscopic Treatment of Posterior Shoulder Instability. The American Journal of Sports Medicine. 2005. DOI: 10.1177/0363546505278301

[186] A Modified Capsular Shift for Atraumatic Anterior-Inferior Shoulder Instability. The American Journal of Sports Medicine. 2005. DOI: 10.1177/0363546504272685

[189] Editorial Commentary: Results of Biplanar Fluoroscopy With 3‐Dimensional Analysis in Patients With Rotator Cuff Tears Challenge the Concept of Superior Translation of the Humeral Head and Must Be Interpreted With Caution. Arthroscopy. 2016. DOI: 10.1016/j.arthro.2015.12.031

[190] Antero-inferior glenohumeral instability is associated with an abnormal position of the coracoid process. JSES International. 2026. DOI: 10.1016/j.jseint.2026.101785

[192] Outcomes of arthroscopic stabilization for posterior shoulder instability: a systematic review. Journal of Shoulder and Elbow Surgery. 2024. DOI: 10.1016/j.jse.2024.04.006

[193] Multidirectional instability of the glenohumeral joint: Etiology, classification, assessment, and management. Journal of Hand Therapy. 2017. DOI: 10.1016/j.jht.2017.03.005

[194] Influence of pelvic position on shoulder range of motion. BMC Musculoskeletal Disorders. 2025. DOI: 10.1186/s12891-025-08280-0

[195] Moment arms of the coracobrachialis and short head of biceps following a Latarjet procedure: a modeling study. Journal of Shoulder and Elbow Surgery. 2024. DOI: 10.1016/j.jse.2023.10.011

[196] Increased superior translation following multiple simulated anterior dislocations of the shoulder. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-07257-z

[197] Acromioclavicular joint ligamentous system contributing to clavicular strut function: a cadaveric study. Journal of Shoulder and Elbow Surgery. 2013. DOI: 10.1016/j.jse.2013.01.004

[198] Outcomes of the Latarjet Procedure Versus Free Bone Block Procedures for Anterior Shoulder Instability: A Systematic Review and Meta-analysis. The American Journal of Sports Medicine. 2020. DOI: 10.1177/0363546520925833

[199] Dynamic anterior stabilization of the shoulder using buttons. JSES International. 2024. DOI: 10.1016/j.jseint.2024.06.016

[201] Imaging Techniques for the Evaluation of Glenohumeral Instability. The American Journal of Sports Medicine. 2000. DOI: 10.1177/03635465000280032501

[202] Rockwood And Matsen S The Shoulder. Fractures, Dislocations, and Acquired Problems of the Shoulder in Children > Subscapularis Tears.

[205] Direct and indirect costs associated with nonoperative treatment for shoulder instability: an observational study in 132 patients. Shoulder & Elbow. 2018. DOI: 10.1177/1758573218773543

[206] Complications Related to Latarjet Shoulder Stabilization: A Systematic Review. The American Journal of Sports Medicine. 2021. DOI: 10.1177/03635465211042314

[208] A new classification of glenoid bone loss to help plan the implantation of a glenoid component before revision arthroplasty of the shoulder. The Bone & Joint Journal. 2016. DOI: 10.1302/0301-620x.98b3.36664

[209] Reproducibility and Reliability of the Snyder Classification of Superior Labral Anterior Posterior Lesions Among Shoulder Surgeons. The American Journal of Sports Medicine. 2011. DOI: 10.1177/0363546510392332

[210] Development and reliability testing of the frequency, etiology, direction, and severity (FEDS) system for classifying glenohumeral instability. Journal of Shoulder and Elbow Surgery. 2011. DOI: 10.1016/j.jse.2010.10.027

[212] Influence of Bony Defects on Preoperative Shoulder Function in Recurrent Anteroinferior Shoulder Instability. The American Journal of Sports Medicine. 2016. DOI: 10.1177/0363546515626541

[214] The Epidemiology and Natural History of Anterior Shoulder Instability. Current Reviews in Musculoskeletal Medicine. 2017. DOI: 10.1007/s12178-017-9432-5

[215] Female Patients Undergoing Latarjet Surgery Show Similar 2‐Year Secondary Surgery Rates but Greater Risk of Emergency Department Visits Compared With a Matched Cohort of Male Patients. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.02.043

[217] Three-Dimensional Characterization of Glenoid Defects in Failed Shoulder Arthroplasties. Journal of Shoulder and Elbow Surgery. 2026. DOI: 10.1016/j.jse.2026.04.002

[219] Posterior Labral Repair With Capsular Plication Shows Enduring Mid-Term Outcomes and Return to Sports With Low Recurrence Rates. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2025. DOI: 10.1016/j.arthro.2025.07.040

[220] Rockwood And Matsen S The Shoulder. Arthroscopic Management of Prearthritic and Arthritic Conditions of the Shoulder and the Postarthroplasty Shoulder > Internal Impingement.

[221] Long‐term outcome of arthroscopic remplissage in addition to the classic Bankart repair for the management of recurrent anterior shoulder instability with engaging Hill–Sachs lesions. Knee Surgery, Sports Traumatology, Arthroscopy. 2018. DOI: 10.1007/s00167-018-5261-3

[224] Treatment of Posterior Shoulder Instability in National Hockey League Players: A Survey of NHL Team Physicians. Orthopaedic Journal of Sports Medicine. 2026. DOI: 10.1177/23259671261440208

[226] High Variability in Standardized Outcome Thresholds of Clinically Important Changes in Shoulder Instability Surgery: A Systematic Review. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.07.039

[227] British Elbow and Shoulder Society practice guidelines: Rehabilitation following traumatic anterior shoulder dislocation (post-operative and non-operative care). Shoulder & Elbow. 2026. DOI: 10.1177/17585732261439731

[228] Variability of Outcome Reporting Following Arthroscopic Bankart Repair in Adolescent Athletes: A Systematic Review. Arthroscopy. 2018. DOI: 10.1016/j.arthro.2017.10.041

[229] Minimum 10-Year Clinical Outcomes After Arthroscopic Capsulolabral Repair for Isolated Posterior Shoulder Instability. The American Journal of Sports Medicine. 2023. DOI: 10.1177/03635465231162271

[230] Intraoperative anterior shoulder dislocation during ulnar nerve transposition: a case report. Journal of Shoulder and Elbow Surgery. 2020. DOI: 10.1016/j.jse.2020.04.012

[231] Rockwood And Matsen S The Shoulder. Arthroscopic Management of Prearthritic and Arthritic Conditions of the Shoulder and the Postarthroplasty Shoulder > EVALUATION OF THE OVERHEAD ATHLETE.

[232] Treatment after traumatic shoulder dislocation: a systematic review with a network meta-analysis. British Journal of Sports Medicine. 2018. DOI: 10.1136/bjsports-2017-098539

[234] Posterior Shoulder Instability. Magnetic Resonance Imaging Clinics of North America. 2020. DOI: 10.1016/j.mric.2019.12.005

[235] Posterior Shoulder Instability in Athletes: An Analysis of the MOON Shoulder Stabilization Cohort. Arthroscopy. 2017. DOI: 10.1016/j.arthro.2017.04.088

[236] Rockwood And Matsen S The Shoulder. Fractures, Dislocations, and Acquired Problems of the Shoulder in Children > RECURRENT DISLOCATION > History.

[238] Type V superior labral anterior–posterior tears results in lower rates of return to play. Knee Surgery, Sports Traumatology, Arthroscopy. 2021. DOI: 10.1007/s00167-020-06388-5

[239] An Algorithmic Approach to the Management of Shoulder Instability. JAAOS: Global Research and Reviews. 2019. DOI: 10.5435/jaaosglobal-d-19-00168

[240] Glenohumeral capsular injury rate in patients with glenohumeral instability: a systematic review and meta-analysis. JSES Reviews, Reports, and Techniques. 2024. DOI: 10.1016/j.xrrt.2024.08.004

[241] It’s Not All About Redislocation: A Systematic Review of Complications After Anterior Shoulder Stabilization Surgery. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518810711

[242] Arthroscopic Posterior Bankart Repair: Risk Factors for Recurrence of Instability. The American Journal of Sports Medicine. 2026. DOI: 10.1177/03635465251403499

[243] Results of treatment of luxatio erecta (inferior shoulder dislocation). Journal of Shoulder and Elbow Surgery. 2010. DOI: 10.1016/j.jse.2009.07.062

[245] Rehabilitation following shoulder arthroscopic stabilisation surgery: A survey of UK practice. Shoulder & Elbow. 2023. DOI: 10.1177/17585732231154889

[246] Shoulder Instability in the Military. Clinics in Sports Medicine. 2014. DOI: 10.1016/j.csm.2014.06.006

[248] Ten-year follow-up of acute arthroscopic Bankart repair for initial anterior shoulder dislocation in young patients. Orthopaedics & Traumatology: Surgery & Research. 2015. DOI: 10.1016/j.otsr.2015.09.029

[250] Campbell S Operative Orthopaedics 4 Volume Set. RECONSTRUCTIVE PROCEDURES OF THE SHOULDER AND ELBOW IN ADULTS > INTRAOPERATIVE COMPLICATIONS > Table 12.4.

[251] Outcomes following arthroscopic Bankart repair in female patients. Journal of Shoulder and Elbow Surgery. 2020. DOI: 10.1016/j.jse.2019.12.012

[252] Prevalence Comparison of Accompanying Lesions between Primary and Recurrent Anterior Dislocation in the Shoulder. The American Journal of Sports Medicine. 2010. DOI: 10.1177/0363546510371607

[253] BESS/BOA patient care pathways: Atraumatic shoulder instability. Shoulder & Elbow. 2018. DOI: 10.1177/1758573218815002

[254] Radiofrequency capsular shrinkage for voluntary shoulder instability. Journal of Shoulder and Elbow Surgery. 2007. DOI: 10.1016/j.jse.2005.11.011

[255] Surgical interventions for anterior shoulder instability in adults. Cochrane Database of Systematic Reviews. 2009. DOI: 10.1002/14651858.cd005077.pub2

[256] Increased Glenoid Index as a Risk Factor for Pediatric and Adolescent Anterior Glenohumeral Dislocation: An MRI-Based, Case-Control Study. Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/2325967120986139

[257] The importance of CT for the pre-operative surgical planning in recurrent anterior shoulder instability. Archives of Orthopaedic and Trauma Surgery. 2012. DOI: 10.1007/s00402-012-1656-7

[258] The Management of Acute Traumatic Primary Anterior Shoulder Dislocation in Young Adults. Shoulder & Elbow. 2010. DOI: 10.1111/j.1758-5740.2010.00083.x

[260] Risk Factors for Recurrent Anterior Glenohumeral Instability Following a Primary Latarjet Procedure: A Prospective Analysis of 358 Patients. Orthopaedic Journal of Sports Medicine. 2020. DOI: 10.1177/2325967120s00378

[262] An Age-Based Approach to Anterior Shoulder Instability in Patients Under 40 Years Old: Analysis of a US Population. The American Journal of Sports Medicine. 2019. DOI: 10.1177/0363546519886861

[263] Imaging Quantification of Glenoid Bone Loss in Patients With Glenohumeral Instability: A Systematic Review. American Journal of Roentgenology. 2019. DOI: 10.2214/ajr.18.20504

[264] Iliac bone-block autograft for posterior shoulder instability. Orthopaedics & Traumatology: Surgery & Research. 2009. DOI: 10.1016/j.otsr.2008.09.008

[265] Arthroscopic lavage reduced the recurrence rate following primary anterior shoulder dislocation. Knee Surgery, Sports Traumatology, Arthroscopy. 1999. DOI: 10.1007/s001670050146

[267] Anterior shoulder instability in patients older than 40 years treated with arthroscopic Bankart repair. Journal of Shoulder and Elbow Surgery. 2025. DOI: 10.1016/j.jse.2024.09.022

[269] Anterior shoulder instability: a review of pathoanatomy, diagnosis and treatment. Current Reviews in Musculoskeletal Medicine. 2011. DOI: 10.1007/s12178-011-9092-9

[271] Imaging of shoulder instability. Quantitative Imaging in Medicine and Surgery. 2017. DOI: 10.21037/qims.2017.08.05

[274] Campbell S Operative Orthopaedics 4 Volume Set. RECONSTRUCTIVE PROCEDURES OF THE SHOULDER AND ELBOW IN ADULTS > INSTABILITY.

[275] Posterior Labral Injury and Glenohumeral Instability in Overhead Athletes: Current Concepts for Diagnosis and Management. Journal of the American Academy of Orthopaedic Surgeons. 2020. DOI: 10.5435/jaaos-d-19-00535

[279] Campbell S Operative Orthopaedics 4 Volume Set. RECONSTRUCTIVE PROCEDURES OF THE SHOULDER AND ELBOW IN ADULTS > COMPLICATIONS OF SHOULDER ARTHROPLASTY.

[283] A comparison of magnetic resonance arthrography and arthroscopic findings in the assessment of anterior shoulder dislocations. Skeletal Radiology. 2014. DOI: 10.1007/s00256-014-2080-6

[287] Comparative Analysis of 3D MRI and CT in Assessing Static Bone Loss and Dynamic Bipolar Interaction in Glenohumeral Instability. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/23259671251343325

[288] Poster 16: Comparative Analysis of 3D MRI and CT in Assessing Static Bone Loss and Dynamic Bipolar Interaction in Glenohumeral Instability. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/2325967125s00129

[289] MRI augmented with novel artificial intelligence system is superior to CT in shoulder instability. JSES International. 2026. DOI: 10.1016/j.jseint.2025.101440

[290] Imaging Signs of Posterior Glenohumeral Instability. American Journal of Roentgenology. 2009. DOI: 10.2214/ajr.07.3849

[292] Acute Versus Delayed MRI Imaging and Associated Pathology in Traumatic Shoulder Dislocations. Orthopaedic Journal of Sports Medicine. 2017. DOI: 10.1177/2325967117s00360

[293] Interest in the glenoid hull method for analyzing humeral subluxation in primary glenohumeral osteoarthritis. Journal of Shoulder and Elbow Surgery. 2017. DOI: 10.1016/j.jse.2017.01.027

[295] Open Repair Reduced Recurrent Dislocation More Than Conservative Treatment After Traumatic Anterior Shoulder Dislocation. The Journal of Bone & Joint Surgery. 2007. DOI: 10.2106/jbjs.8908.ebo1

[297] Editorial Commentary: Patients May Have Posterior Glenoid Labral Tears in the Absence of Instability or Magnetic Resonance Imaging Findings. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2023.07.004

[298] Lower Recurrence Rates With Arthroscopic Latarjet Compared to Arthroscopic Bankart Repair in Shoulder Instability: A Long-Term Matched Pair Study. Journal of ISAKOS. 2025. DOI: 10.1016/j.jisako.2025.100765

[301] Imaging methods for quantifying glenoid and Hill-Sachs bone loss in traumatic instability of the shoulder: a scoping review. BMC Musculoskeletal Disorders. 2015. DOI: 10.1186/s12891-015-0607-1

[303] Superior-capsular elongation and its significance in atraumatic posteroinferior multidirectional shoulder instability in magnetic resonance arthrography. Acta Radiologica. 2010. DOI: 10.3109/02841850903524421

[304] Rockwood And Matsen S The Shoulder. Fractures, Dislocations, and Acquired Problems of the Shoulder in Children > TYPES OF GLENOHUMERAL INSTABILITY > Circumstances of Instability.

[305] Poster 105: MRI Demonstrates Similar Diagnostic Value to MR Arthrogram for Determining Labral Tear Extent up to 2 Weeks Following Shoulder Dislocation. Orthopaedic Journal of Sports Medicine. 2024. DOI: 10.1177/2325967124s00075

[307] Evaluation of glenoid morphology and bony Bankart lesion in shoulders with traumatic anterior instability using zero echo time magnetic resonance imaging. JSES International. 2024. DOI: 10.1016/j.jseint.2024.03.003

[309] Humeral head deviation and velocity in multidirectional instability of the glenohumeral joint: a cine magnetic resonance imaging study. JSES International. 2026. DOI: 10.1016/j.jseint.2025.101419

[310] Magnetic resonance imaging predictors of shoulder instability in adolescents. Pediatric Radiology. 2018. DOI: 10.1007/s00247-018-4318-2

[311] Posterior Humeral Avulsion of the Glenohumeral Ligament (Posterior HAGL) Lesions: Correlation Between MRI, Clinical, and Arthroscopic Findings (SS‐07). Arthroscopy. 2007. DOI: 10.1016/j.arthro.2007.03.020

[312] Arthrotomography of the glenoid labrum in shoulder instability.. The Journal of Bone & Joint Surgery. 1982. DOI: 10.2106/00004623-198264040-00005

[313] Arthroscopic Bankart repair: results and risk factors of recurrence of instability. Knee Surgery, Sports Traumatology, Arthroscopy. 2010. DOI: 10.1007/s00167-010-1105-5

[314] Simultaneous bilateral posterior dislocation of the shoulder: diagnostic problems and management. Knee Surgery, Sports Traumatology, Arthroscopy. 2006. DOI: 10.1007/s00167-006-0066-1

[315] Two‐Year Outcomes of Open Shoulder Anterior Capsular Reconstruction for Instability From Severe Capsular Deficiency. Arthroscopy. 2011. DOI: 10.1016/j.arthro.2011.07.002

[317] Quality of life following an open Latarjet-Bristow procedure in a general population with recurrent anterior shoulder instability. JSES International. 2023. DOI: 10.1016/j.jseint.2022.12.003

[318] Paper 11: Return to Sport Testing vs Time-Based Clearance in Posterior Shoulder Instability. Orthopaedic Journal of Sports Medicine. 2022. DOI: 10.1177/2325967121s00549

[319] Paper 29: Return to Sport Testing vs Time-Based Clearance in Posterior Shoulder Instability. Orthopaedic Journal of Sports Medicine. 2022. DOI: 10.1177/2325967121s00593

[320] Return to Sport as Outcome Measure for Shoulder Instability: Surprising Findings in Non-Operative Management in a High School Athlete Population. Orthopaedic Journal of Sports Medicine. 2017. DOI: 10.1177/2325967117s00284

[321] Impact of prior anterior instability on shoulder arthroplasty outcomes: a systematic review. JSES International. 2022. DOI: 10.1016/j.jseint.2022.08.012