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Hip instability and microinstability

172 citationsUpdated Sep 2026

Overview

Hip instability and microinstability frequently coexist with femoroacetabular impingement (FAI) morphologic characteristics [1]. The dominant deformity in developmental hip dysplasia is deficient anterolateral acetabular coverage, which results in structural instability and acetabular rim overload [31]. Hips at greatest risk of failure present with advanced arthrosis or a combination of impingement and instability preoperatively [3]. Evaluation of recurrent hip instability requires a systematic approach involving a thorough history, physical examination, and targeted radiographic evaluation [2]. While the long-term prognosis for symptomatic moderate dysplasia (lateral center-edge angle <15°) treated nonsurgically is very poor [31], surgical intervention offers distinct pathways. Hip arthroscopy has expanded rapidly, addressing pathology in the central, peripheral, and peritrochanteric compartments, including capsular laxity associated with instability [23].

Surgical outcomes vary by procedure and patient phenotype. Hip arthroscopy for FAI yields increased patient-reported outcome measures, with most patients reaching critical thresholds of clinical improvement [76]. Complication rates for hip arthroscopy across all indications are generally less than 1.5% [15]. Both hip arthroscopy and open surgical hip dislocation demonstrate excellent and equivalent hip survival rates at medium-term follow-up [79]. Open surgical hip dislocation benefits patients with complex pathology who are not candidates for arthroscopy, showing high survivorship and improved outcomes [18]. In patients with generalized ligamentous laxity, hip arthroscopy yields favorable outcomes and survivorship at 5-year minimum follow-up comparable to those without laxity [39]. However, some patients suffering instability after hip arthroscopy for FAI do not show improved outcomes [35]. Routine intraoperative repair of the articular capsule is recommended to positively influence short-term functional results [199], and capsular preservation and closure should remain universal, particularly for phenotypes requiring maximum surgical stability [4].

For borderline dysplasia, durable outcomes with low revision rates are expected after hip arthroscopy involving labral preservation and careful capsular closure [17]. Long-term outcomes in borderline dysplasia patients are favorable, with equivalent results to nondysplastic cohorts [20]. Patients with dysplasia achieve similar outcomes and survivorship to nondysplastic patients 10 years after hip arthroscopy for FAI, with a high survivorship rate of 91% at minimum 10-year follow-up [42]. Conversely, arthroscopic management of mild to moderate acetabular dysplasia shows inferior good/excellent results and higher failure rates compared to an FAI cohort [204]. Consequently, hip arthroscopy for borderline hip dysplasia has a role with narrow indications, particularly in revision settings where the root cause of failure must be identified [74]. Instability-driven symptoms in borderline dysplasia primarily indicate periacetabular osteotomy [74]. The Bernese PAO is a mainstay of surgical treatment for developmental hip dysplasia [31]. Concomitant hip arthroscopy and PAO appears safe and effective with favorable mid-term outcomes [21]. PAO used as a salvage procedure for instability recalcitrant to prior arthroscopy demonstrates substantial improvement in patient-reported outcome measures and radiographic correction of acetabular coverage [80]. The shelf acetabuloplasty technique offers limited invasiveness while allowing comprehensive management of hip instability related to moderate dysplasia [16]. Ligamentum teres reconstruction is predominantly supported for patients experiencing refractory instability following previous hip preservation procedures [75]. In certain cases, hip arthroscopy can be cost-effective given a long enough duration of benefit and appropriate patient selection [73]. Patients 40 years and older who underwent primary hip arthroscopy with labral repair demonstrated a hip preservation rate of 78%, significant and durable improvement in PROMs, and high rates of satisfaction at a minimum 10-year follow-up [203]. Additional studies are needed to determine protective or adaptive factors in patients with abnormal anatomy who do not develop early OA and to determine whether joint preserving hip surgery extends the life of the native hip joint [6].

Anatomy & Pathophysiology

Bony Anatomy & Morphology

The hip is a multiaxial joint connecting the axial skeleton to the lower extremity via the articulation of the pelvis and femur [99]. The hemipelvis consists of the ilium, ischium, and pubis, which unite at the triradiate cartilage within the concave acetabulum [99]. The acetabulum features an articular crescent-moon-shaped lunate surface and a nonarticular central fossa serving as the attachment point for the ligamentum teres [99]. Inferiorly, the acetabulum is incomplete, forming a notch through which vital blood vessels and nerves pass to supply the joint [99]. The femoral head forms two-thirds of a sphere, with a central depression from which the ligamentum teres extends to connect to the acetabular notch [99]. The femoral neck-shaft angle averages 125°, positioning the head and neck more perpendicular to the acetabulum in a neutral position to allow greater mobility [99]. Normal version, defined as the head-neck angle in the frontal plane, averages 15 to 20° [99]. The angular projection of the femoral head and neck relative to the obliquely placed acetabulum permits rotary movements and prevents impingement [99].

Acetabular dysplasia is defined by a lateral center-edge angle (LCEA) of <25° on the AP pelvic radiograph, while an LCEA between 20° and 25° is considered borderline dysplasia [145]. This undercoverage of the femoral head by a relatively shallow acetabular rim is the origin of the association between hip dysplasia and hip microinstability [145]. Lack of acetabular coverage can lead to excessive femoral head micromotion against the acetabulum, resulting in hip microinstability [145]. This microinstability may cause an overload on acetabular structures, leading to compensatory labral hypertrophy and sometimes rim fractures [145]. A lower center-edge angle or larger Tönnis angle increases the risk for severe cartilage damage to the femoral head [145]. Specifically, patients with a lateral center-edge angle of 25° were 3.57 times more likely to have severe cartilage damage to the femoral head [145]. Hip dysplasia is a pathoanatomic osseous morphology associated with hip instability that may, in part, be due to hip capsular thickness [5].

Femoroacetabular impingement (FAI) involves distinct structural abnormalities producing repetitive impingement between the acetabulum and the femoral head-neck junction [24]. Cam impingement refers to femoral-based deformities, such as an aspherical femoral head or reduced head-neck offset, resulting in repetitive abutment of the acetabular rim and femoral head-neck junction [9]. Pincer impingement describes acetabular-based deformities, such as acetabular retroversion or acetabular protrusio, creating abnormal abutment of the acetabular rim and femoral head-neck junction [9]. Combined cam and pincer deformities are common in FAI [24]. The contemporary theory of FAI holds that morphologic abnormalities of the femoral head and/or acetabulum result in abnormal contact between the femoral neck and head and the acetabular margin [29]. This abnormal contact leads to supraphysiologic stress, causing tearing of the labrum and avulsion of the underlying cartilage region [29]. Continued abnormal contact results in further deterioration and wear of the articular cartilage, with the eventual onset of arthritis [29]. Osteophyte formation at the femoral head-neck junction resulting from osteoarthritis can restrict joint motion, leading to secondary FAI [29]. Impingement abnormalities can cause labral tears, degeneration, or ossification [24], acetabular cartilage delamination [24], and secondary osteoarthritis [24].

FAI can contribute to the development of hip microinstability due to the altered relationship between the femoral head and acetabulum [145]. Pincer and/or cam impingement can lead to levering of the femoral head posteriorly, resulting in hip microinstability and, in extreme cases, posterior hip dislocation [145]. High rates of FAI morphologic characteristics are present in patients with hip instability [1]. Both acetabular and femoral morphology are critical to understanding FAI, as the complex interplay of versions influences outcomes and the presence of asymptomatic lesions [63]. Hip-combined rotational morphology has little short-term impact on clinical outcomes after hip arthroscopy in FAIS patients [33]. Increased cam morphology remained a significant contributor to reduced internal rotation but did not affect hip flexion [130]. Hip impingement in those with FAIS may routinely occur at hip flexion angles below 90° in neutral rotation, with males engaging at higher flexion angles than females [161]. Despite simulating lower degrees of hip flexion and internal rotation, increased stress and a shift in contact location were observed in the simulated models of FAI [122].

Soft Tissue Anatomy & Stability

The hip joint is relatively stable due to its ball-and-socket bony anatomy and soft-tissue constraints, including the labrum, capsule, and ligamentum teres [47]. The acetabular labrum is a triangular fibrocartilaginous ring attached firmly to the acetabular rim, encompassing nearly the entire acetabulum except for the most inferior aspect, which is bridged by the transverse acetabular ligament [59]. The labrum deepens the acetabulum, increases coverage of the femoral head, and plays a role in shock absorption, joint lubrication, and pressure distribution [59]. Its most critical role may be the creation of a negative pressure seal with the femoral head, which aids in joint stability [59]. Removal of the labrum leads to a shift in the femoral contact point toward the acetabular rim, a decrease in intra-articular fluid pressurization, and a loss of lateral restraint to femoral head motion [59]. Furthermore, removal of the labrum increases contact stresses between the articular cartilage of the femoral head and the acetabulum by 92% [59]. Only the external one-third of the labrum contains blood vessels, leaving the majority of the structure avascular and limiting its healing ability following injury [99]. The labrum is highly innervated, with the presence of both mechanoreceptors and nociceptors [99].

The hip is surrounded by a dense fibrous capsule extending from the periphery of the acetabulum to the intertrochanteric line of the femoral neck [99]. The capsule enhances joint stability by preventing translation of the femoral head in the acetabulum [99]. Three main ligaments support the hip: * Iliofemoral ligament: The thickest and strongest, it functions to limit external rotation, while its lateral arm limits extension of the joint [99]. It becomes taut in full extension, preventing anterior dislocation and hyperextension of the hip [100]. It has been reported to resist external rotation in hip flexion and both external and internal rotation in hip extension [178]. * Ischiofemoral ligament: Provides support posteriorly and restricts internal rotation motion [99]. It resists internal rotation in flexion or extension [178]. * Pubofemoral ligament: Acts to limit abduction of the joint [99]. It resists external rotation in extension or abduction [178].

Deep fibers from the iliofemoral, ischiofemoral, and pubofemoral ligaments merge to form the zona orbicularis, which circumvents the femoral neck [99]. The twisted orientation of the hip ligaments provides a screw mechanism for the hip in full extension [100].

The ligamentum teres originates in the cotyloid fossa and attaches on the fovea of the femoral head [100]. It transmits an arterial branch of the posterior division of the obturator artery to the femoral head, which is less significant in adults [96]. The ligamentum teres appears to play a secondary role to other soft-tissue restraints, having been shown to restrict the motion of the femoral head [181]. However, isolated tears of the ligamentum teres have been found in hip dysplasia, in which it may play a more prominent role in stabilization [181].

Pathophysiology of Microinstability

Hip microinstability refers to the femoral head micromotion within the acetabulum, which is a prolonged phenomenon that leads to cartilage damage and eventually osteoarthritis of the hip [47]. Current evidence supports that the hip capsule is the structure mainly implicated in hip microinstability [52]. Loss of the seal between the labrum and the femoral head may cause increased movement of the femoral head or microinstability [52]. Hip microinstability is characterized by a progressive onset with pain, disability, and a feeling of giving way in the hip [52]. The diagnosis of microinstability without the presence of bony abnormality is described as difficult because signs and symptoms may be subtle, and there is no definitive preoperative diagnostic test, examination finding, or imaging modality that is pathognomic for hip microinstability [26]. Nevertheless, there has been significant growth in evidence to support hip microinstability as a real entity, even without the presence of bony deficiency [26].

Hip instability has gained recognition as an important cause of hip pathology, with causes including incongruency of the articular surfaces due to dysplasia and/or impingement, joint capsule pathology, labral pathology, ligamentum teres tears, ligamentous laxity, muscular imbalance, and tendon tears [70]. The term "microinstability" may be more appropriate for hip instability because symptoms are generally less tangible than in other joints, where patients commonly complain of giving way, subluxation, and recurrent dislocations [70]. In the setting of hip dysplasia, the individual is much more reliant on soft-tissue structures to stabilize the hip [181]. The athlete with hip microinstability may report mechanical symptoms and feelings of instability, especially in hip positions that rely more on soft-tissue restraint such as hip extension and external rotation [181]. Secondary iliopsoas tendinitis from strain on the iliopsoas as it attempts to stabilize the anterior hip joint can develop in patients with hip microinstability [181]. The log-roll external rotation test may show capsular laxity, with diminished spring back during external rotation [181].

Sports that require a great deal of hip torsion can lead to capsule attenuation and laxity secondary to repetitive microtrauma [59]. Attenuation of the capsule leads to microinstability of the joint, in which the femoral head subluxates anteriorly and rides on the anterior superior labrum [59]. Microinstability can occur in patients with collagen disorders such as Ehlers-Danlos syndrome, Marfan syndrome, and Down syndrome [59]. Damage to any aspect of the capsular complex may result in increased microinstability [178]. Capsular stretching can be the result of inherent tissue laxity or anatomic stretching due to pathologic motion of its bony attachment sites, such as in hips with FAI or dysplasia [178]. A 2018 study demonstrated a significant increase in femoral head translation when incisions were made in the capsule complex [178]. A 2019 study showed a significant increase in femoral head displacement following cyclical stretching of the capsule [178]. Biomechanical evidence supports closure of the capsule after hip arthroscopy to reverse the significant effects of capsulotomy [134]. The puncture capsulotomy technique preserves the native anatomy and biomechanics of the hip joint by leaving the iliofemoral ligament intact [143]. This technique eliminates the risk of gross anterior dislocation and avoids postoperative range-of-motion restrictions associated with traditional capsulotomy [143]. The management of the capsule is critical and must allow for improved exposure without compromising stability and kinematics of the hip [8].

The acetabular labrum, the ligamentum teres, and the joint capsule play critical secondary roles to bony restraint in hip microinstability [53]. Soft-tissue structures, including the ligamentum teres, play a key role in maintaining stability, especially in the setting of abnormal bony morphology [53]. Appropriate capsular management, including capsular repair and plication in indicated cases, is proving to be a key step in preserving or establishing hip stability and optimizing surgical outcomes [53]. The acetabular labrum is a critical structure and should be repaired or reconstructed whenever possible to preserve its function, especially the negative suction seal function [53]. Hip microinstability is an increasingly recognized source of pain and instability because of soft-tissue restraint incompetency in the borderline dysplastic hip [53]. Tears of the ligamentum teres are a source of pain in the hip and require a high index of suspicion to make the diagnosis [53]. Ligamentum teres reconstruction in instability cases may prove to be a useful adjunct along with capsular plication in certain settings but is still unproved at this point [53]. When patients present for revision arthroscopy with persistent pain and significant delay in achieving postoperative milestones, defects in the capsule should be suspected or the seal between the femoral head and the labrum may no longer be intact, which results in microinstability [55]. Athletes who participate in sports that include hyperextension may be more likely to have microinstability, especially those with hip dysplasia or connective tissue disorders [55].

Kinematics & Biomechanics

The osteochondral layer includes the femur, pelvis, and acetabulum, which provide joint congruence and normal joint kinematics [19]. Structural variations resulting in static overload include lateral or anterior acetabular undercoverage/dysplasia, femoral anteversion, and femoral valgus that lead to abnormal stress and asymmetric loads between the femoral head and acetabular socket in the axially loaded position [19]. When the functional range of motion is greater than the amount of physiological motion allowed by the hip, forceful anterior contact occurring at the end range of internal rotation may lead to dynamic instability in the form of subtle posterior hip subluxation [19]. Dynamic instability occurs as the femoral head levers out of the hip socket due to mechanical stresses leading to reactive hip pain related to insufficient congruency or impingement [19]. Any alteration to joint morphology or function can place the hip at risk for pathology [22]. The hip is a complex multiaxial joint capable of producing large forces and moving the thigh through large ranges of motion [22].

Individual and postural variations in physiologic pelvic tilt affect joint contact pressure in the hip [126]. At 70 and 90 degrees of hip flexion, a combined change in 3D pelvic alignment of 5 degrees was more effective in improving hip maximum internal rotation than a 10-degree change in sagittal tilt only [150]. The mechanical loading on the acetabular cartilage in cam-type hips is left unchanged regardless of labral size during walking and deep flexion [165]. FAI participants altered their walking kinematics and kinetics, especially during contralateral foot-strike, as a protective mechanism, which resulted in reduced psoas major and iliacus muscle force and anterosuperior hip contact force estimations [144]. No biomechanical differences existed between symptomatic FAI groups and asymptomatic groups during level walking, yet hamstring and gluteus maximus activation differed [182]. The femoral head translates the same under bodyweight loading as previously observed during supine exam, showing the inherent stability of the hip with no history of surgery or symptomatic pathology [68].

Clinical Evaluation & Outcomes

Patient-reported outcome measures and diagnostic imaging are the most frequently reported outcomes, while measures of hip strength and range of motion are underreported [7]. Current surgical outcomes for FAI are limited to mid-term follow-up time frames with inconsistent reporting [7]. A thorough evaluation of the hip must include a comprehensive medical and surgical history focused on the hip joint, surrounding soft tissues, and associated structures, followed by a physical examination in multiple positions and gait assessment to distinguish between intra-articular and extra-articular contributors to hip pain [13]. There is no recognized systematic hip evaluation protocol to help prevent a missed diagnosis [19]. A "layered approach" to understanding the underlying etiological factors contributing to pain around the hip joint includes the osteochondral, intra-articular, muscular, and neural layers [19].

Classification

Clinical Definitions and Consensus

FAI Syndrome: Femoroacetabular impingement (FAI) syndrome is defined as a motion-related clinical disorder of the hip characterized by a triad of symptoms, clinical signs, and imaging findings [28]. The precise definition of "impingement" remains elusive in current literature; while dynamic MRI holds potential to better define hip impingement, it is not yet optimized for widespread clinical use [88].

Hip Microinstability: Hip microinstability is a newly defined hip pathology identified in young athletes [25].

Pathoanatomic Morphology

Cam and pincer hips are distinct pathoanatomic entities [245]. The three primary factors involved in the preservation of the hip joint include femoroacetabular impingement, hip dysplasia/instability, and femoral torsion abnormalities [90]. An isolated assessment of the lateral center-edge angle (LCEA) is an oversimplistic approach that may jeopardize appropriate classification and provide insufficient data to guide the treatment of hips with additional features of dysplasia and instability [61]. Classifying acetabular dysplasia into three groups based on the plane of instability could optimize the planning of periacetabular osteotomy (PAO) by providing a better understanding of the three-dimensional deformity [221].

Diagnostic Evaluation

A comprehensive approach to the interpretation of magnetic resonance examination of the hip includes optimal sequences and planes for identifying key pathology and quantifying bony morphology [10]. For determining the presence of a crossover sign, advanced 3D CT-generated hip models improve inter- and intra-observer agreement [36]. A significant association exists between acetabular labral tears and structural abnormalities of the hip, with 87% of patients having at least one abnormality detectable on conventional radiographs [11].

Chondrolabral and Soft Tissue Classification

New Bern Chondrolabral Classification: This is a novel classification system for damage to the hip cartilage and labrum, developed to address inadequate reliability in established systems [228]. Acetabular chondral flap type visualized during hip arthroscopy correlates with radiographic markers of hip impingement and hip instability [86]. Understanding hip disorder-specific chondral damage patterns may be useful for the development of an arthroscopic classification of hip disorders and may lead to the establishment of treatment guidelines [177].

Beck Classification: The Beck classification of transition zone cartilage is used to grade chondrolabral junction (CLJ) damage, with grades 0 to 2 stratified as mild and grades 3 and 4 as severe [238]. In joint-preserving hip surgery, lesions of the ligamentous-fossa-foveolar complex (LFFC) are very common, with 65% of hips showing substantial damage [237].

Risk Stratification and Prognostic Factors

Factors associated with the success or failure of arthroscopic management of FAI are categorized into four types: (1) patient characteristics or clinical history, (2) preoperative patient-reported outcomes (PROs), (3) joint parameters, and (4) operative practices [246]. Patients with borderline hip dysplasia and radiographic evidence of hip instability, as measured by the FEAR index (≥2), may achieve similar improvement in 2-year outcomes compared to those with radiographically stable hips after arthroscopic treatment of FAIS [241].

Clinical Presentation

History and Symptom Characterization

Patients with symptomatic femoroacetabular impingement (FAI) frequently present with activity-related groin pain exacerbated by hip flexion, often reporting difficulty with prolonged sitting, walking, running, or pivoting [24]. The onset of symptoms is typically insidious or follows minor trauma, and mechanical symptoms secondary to labral and articular cartilage disease are common [24]. Anterior groin pain is most associated with intra-articular pathologies, including labral tears, degenerative changes, synovial pathologies, loose bodies, and osteonecrosis [138]. However, anterior pain can also result from extra-articular conditions such as hip flexor strains, iliopsoas snapping syndrome, or femoral stress fractures [138]. Pain along the lateral thigh is often associated with greater trochanteric bursitis, iliotibial band syndrome, or abductor tendon tears or tendinitis [138]. Conversely, pain in the posterior region of the hip and pelvis can result from muscle pathologies such as piriformis syndrome and hamstring muscle tears, or referred pain from the sacroiliac joint or low back [138].

A thorough history is essential to differentiate between common causes of hip pain [22]. Assessing the onset, duration, and location of symptoms, along with factors that exacerbate or alleviate pain, is important for determining the cause of hip pain [138]. Identifying changes to activity type or training regime can help differentiate between hip conditions when there is no known precipitating event [138]. Documenting family history of hip conditions is important because certain genetic conditions, such as Ehlers-Danlos syndrome, can affect the hip [138]. The presence of FAI morphology does not necessarily mean that FAI is the primary source of hip pain; other less common causes, such as osteoid osteoma, should be included in the differential diagnosis when atypical clinical and radiological signs are found [149].

Hip Microinstability

Patients with hip microinstability commonly present with pain of progressive onset [47]. This condition is often seen in athletes who require extreme range of motion, such as dancers [47]. Patients often describe hip or groin pain that has increased over time [55]. Most patients report a feeling of instability or giving way in the hip [55]. The description of giving way during activity is a critical factor in the diagnosis of microinstability [55]. Athletes who participate in sports that include hyperextension may be more likely to have hip microinstability [55]. Patients with hip dysplasia or connective tissue disorders, with or without a history of previous joint dislocation, are especially prone to hip microinstability [55]. When patients present for revision arthroscopy with persistent pain and significant delay in achieving postoperative milestones, defects in the capsule or a compromised seal between the femoral head and labrum resulting in microinstability should be suspected [55].

Hip microinstability may present by itself or in association with other conditions [48]. There is no definitive preoperative diagnostic test, examination finding, or imaging modality that is pathognomic for hip microinstability [26]. The diagnosis of microinstability without the presence of bony abnormality is described as difficult because signs and symptoms may be quite subtle [26]. The term "microinstability" may be more appropriate than "instability" for the hip because symptoms are generally less tangible and do not typically include giving way, subluxation, or recurrent dislocations [70]. Causes of hip instability include incongruency of the articular surfaces due to dysplasia and/or impingement, joint capsule pathology, labral pathology, ligamentum teres tears, ligamentous laxity, muscular imbalance, and tendon tears [70].

Physical Examination

A thorough evaluation of the hip must include a comprehensive medical and surgical history focused on the hip joint, surrounding soft tissues, and associated structures [13]. Physical examination for hip evaluation should be performed in multiple positions and include gait assessment to distinguish between intra-articular and extra-articular contributors to hip pain [13]. Patients with FAI will exhibit restricted hip internal rotation in 90° of flexion [24]. The impingement test (flexion, adduction, internal rotation) will elicit pain in patients with FAI, but the test is not specific for FAI [24]. The clinical impingement sign is challenged as a specific diagnostic test [129].

Physical examination for hip microinstability focuses on stressing the anterior or posterior hip capsule and trying to reproduce the patient's symptoms [48]. The abduction-hyperextension-external rotation test, the prone instability test, and the hyperextension-external rotation test have been shown to aid in the diagnosis of hip microinstability [48]. Patients with hip microinstability typically present a positive anterior impingement sign (pain with flexion, adduction, internal rotation) and/or a positive labral stress test [48]. Both the anterior impingement sign and the labral stress test suggest an intra-articular source of hip pain [48]. Hip strength deficits were common in patients presenting with unilateral symptomatic FAI and occurred most commonly in hip abduction and flexion [137]. Pathologic thickening of the hip capsule may contribute to restricted hip mobility on clinical examination [65]. In the presence of joint hypermobility, muscles may appear tight or restricted when they are actually guarded and overworked as dynamic stabilizers [26]. Individuals with excessive hip external rotation ROM have decreased strength of the hip internal rotators, and those with excessive internal rotation ROM have decreased strength of the hip external rotators [26]. Decreased hip rotational stability and/or strength has been noted in individuals with symptomatic acetabular labral tears [26].

The physical examination for adolescent hip dysplasia should include observation of ambulation to assess for an antalgic gait or a subtle Trendelenburg gait [136]. The impingement test should be performed in adolescent hip dysplasia to determine the likelihood of true symptomatic labral pathology [136]. Lateral hip pain in adolescent hip dysplasia is most often attributed to decreased hip abductor muscle strength and occurs later in the day as fatigue develops [136]. Deep anterior groin pain in adolescent hip dysplasia generally indicates pain originating from the joint itself, such as joint overload, edge-loading of the acetabulum, labral irritation or injury, or labral chondral injury [136]. The Beighton score should be evaluated in patients with combined borderline hip dysplasia and excessive femoral anteversion to assess for instability [166].

Imaging and Diagnostic Findings

Radiographic evidence of FAI is common in active patients with hip complaints [57]. The overall prevalence of radiographic findings consistent with FAI in young patients presenting with hip pain was 60.5% [62]. A significant association exists between acetabular labral tears and structural abnormalities of the hip, with 87% of patients having at least one abnormality detectable on conventional radiographs [11]. Acetabular and femoral osseous abnormalities are commonly associated with labral tears [168]. The AP pelvis view is used to assess acetabular anatomy, including version, acetabular coverage, and femoral head sphericity [24]. Various lateral views, most commonly the 45° Dunn view and frog-leg lateral, can be used to assess femoral head sphericity and head-neck offset [24]. MRI or magnetic resonance arthrography provides information regarding the integrity of the acetabular labrum and articular cartilage [24]. MRI or magnetic resonance arthrography can assess the anatomy of the proximal femur as well as the version of the acetabulum and femur [24]. Sensitivity of MRI or magnetic resonance arthrography to acetabular rim chondral lesions is limited [24]. Low-dose CT with three-dimensional reformats is particularly useful in surgical planning of complex or borderline deformities [24].

An isolated assessment of the lateral center-edge angle (LCEA) is an oversimplistic approach that may jeopardize appropriate classification and provide insufficient data to guide treatment of hips with additional features of dysplasia and instability [61]. Sensitivity, specificity, and intraobserver and interobserver observational consistency for femoroacetabular impingement radiographic diagnosis require confirmation [72]. Until radiologic criteria are confirmed, hip arthroscopic surgeons must rely on expert clinical examination [72]. The diagnostic accuracy of CT-based acetabular sector angles in pincer-type FAI is moderate, with sensitivity of 40%-60% and specificity of 81%-88% [118]. Acetabular morphology exists on a continuum, and the boundary between normal variation and pathological overcoverage is inherently imprecise [118]. Many individuals with elevated intra-articular acetabular sector angle (IAASA) values remain asymptomatic, while others with borderline values develop symptoms [118]. Factors beyond bony morphology, including activity level, labral tissue properties, cartilage quality, and neuromuscular hip control, explain the variability in symptoms among patients with similar radiographic findings [118]. The Warwick Agreement emphasizes the need for concordance between symptoms, clinical signs, and imaging findings for FAI syndrome diagnosis [118].

The presence of apparently abnormal imaging findings in asymptomatic patients is well-known [67]. Patients with asymptomatic contralateral hips with FAI have a 21% risk of developing symptoms [67]. Approximately one in four patients with FAI presents with symptoms in the contralateral hip [69]. 16% of initially asymptomatic contralateral hips will develop symptoms during the next several years [69]. An additional 1 in 4 patients with FAI develops significant symptoms in the contralateral hip in the following 4 years [172]. Decreased hip ligament thickness in patients with dysplasia may contribute to hip instability above and beyond associated acetabular under-coverage [5]. A clinical diagnosis of hip osteoarthritis was found in approximately 22% of young patients undergoing hip arthroscopy within 2 years [54]. The "windshield wiper sign," an osteochondral defect of the anterolateral femoral head, predicts instability and allows planning of combined arthroscopic cartilage therapy and periacetabular osteotomy [51].

Both acetabular and femoral morphology are critical to understanding femoroacetabular impingement and developing patient-specific treatments [63]. The complex interplay of versions influences outcomes and the presence of asymptomatic lesions in FAI [63]. Clinical identification of combined impingement and dysplasia is imperative to potentially improve patient outcomes [146]. Clinicians should evaluate for additional radiographic factors suggestive of instability in patients with combined borderline hip dysplasia and excessive femoral anteversion, as these findings may portend inferior outcomes after arthroscopic treatment in isolation [166]. Open procedures like periacetabular osteotomy are a more reliable option for symptomatic hip instability in patients with combined borderline hip dysplasia and excessive femoral anteversion [166]. Extraarticular FAI is an uncommon source of impingement symptoms, often missed due to prior hip surgery, and seems more common in younger, female patients [167]. Considering the high prevalence of radiographic hip findings reminiscent of FAI in asymptomatic Asian populations, it will be important to determine whether FAI-related morphologic features are a cause of hip pain when considering surgery in Asian patients [163]. Patient-reported outcome measures and diagnostic imaging are the most frequently reported outcomes in FAI studies, while measures of hip strength and range of motion are underreported [7]. As there is a high percentage of overlapping questions between the most commonly used hip-specific patient-reported outcome measures for FAI syndrome, multiple tests may be appropriate for use [30]. A comprehensive approach to interpretation of magnetic resonance examination of the hip includes optimal sequences and planes for identifying key pathology and quantifying bony morphology [10]. The evaluation of the patient with recurrent hip instability should be approached systematically with a thorough history and physical examination, along with a focused and targeted radiographic evaluation as indicated [2]. Imaging findings should complement clinical examination findings to provide the most accurate diagnosis of hip pain [22]. A thorough understanding of normal anatomy and biomechanics is necessary to identify pathology and determine the appropriate course of treatment for hip pain [22].

Investigations

Clinical Evaluation and History: A thorough history is essential to differentiate between common causes of hip pain, with clinical examination tests and imaging findings used to confirm a suspected diagnosis [22]. Patients with symptomatic femoroacetabular impingement (FAI) frequently present with activity-related groin pain exacerbated by hip flexion activities, and report difficulty with prolonged sitting, walking, running, or pivoting [24]. The onset of symptoms is often insidious or follows minor trauma, and mechanical symptoms secondary to labral and articular cartilage disease are common [24]. Physical examination reveals restricted hip internal rotation in 90° of flexion [24]. The impingement test (flexion, adduction, internal rotation) elicits pain in patients with FAI but is not specific for the condition [24]. Evaluation of the patient with recurrent hip instability should be approached systematically with a thorough history and physical examination, followed by a focused and targeted radiographic evaluation [2].

Plain radiography: Conventional radiographs remain critical in the initial imaging evaluation of the hip [46]. A complete hip series usually consists of an anterior-posterior (AP) pelvis, a centered AP hip, a lateral view (frog-leg, cross-table, Dunn 45° or 90°), and a false-profile (Lequesne) view [46]. Acetabular morphology is assessed on AP pelvis radiographs to evaluate overcoverage and undercoverage, while specific views of the hip are used to detect abnormalities of the femoral head-neck junction seen with FAI [46]. The femoral head-neck junction morphology is often assessed using the alpha angle; some studies have shown that radiographs, in particular the Dunn 45° view, may be more accurate for determining the alpha angle measurement than CT or MRI [46]. The "crossover" sign on AP pelvis radiographs indicates acetabular retroversion related to lateralization of the anterior acetabular wall relative to the posterior acetabular wall, although pelvic tilt or rotation may lead to false-positive and false-negative signs [46]. For neutral pelvic tilt on an AP pelvis radiograph, the sacrococcygeal joint should be between 3 and 5 cm above the superior border of the symphysis pubis [46].

The Tönnis angle is defined by the angle of the acetabular sourcil and a line parallel to the transverse pelvis axis, with values between 0° and 10° considered normal [46]. The lateral center-edge angle of Wiberg is the angle between a line from the center of the femoral head perpendicular to the transverse pelvis axis and a second line from the center of the femoral head to the superolateral most point of the acetabulum [46]. Center-edge angles of 20°–40° are considered normal, while angles from 20° to 25° are considered borderline [46]. The femoral head extrusion index is defined by the length of the femoral head that lies beyond the acetabulum as a percentage of the total horizontal width of the femoral head, with values greater than 25% considered abnormal [46]. Coxa profunda is diagnosed when the fossa line touches or is medial to the ilioischial line on an AP pelvis radiograph [46].

Radiographic indicators of FAI are very common among athletes evaluated at the National Football League Scouting Combine subjected to radiographic examination for the clinical suspicion of hip disease [260]. Radiological evidence of symptomatic femoroacetabular impingement was not uncommon in Japanese patients with hip pain, with cam deformity findings being the most common [248]. A narrow posterior joint space on a False Profile radiograph does not correlate with posterior joint cartilage degeneration in hip preservation patients [252]. A computer-assisted analysis of young adult hip radiographs generally demonstrates substantial to excellent levels of interobserver reliability for most parameters [232]. Surgeons experienced in FAI/Dysplasia have higher interrater agreement in making a diagnosis of such hip disorders than other hip surgeons; however, this remains only fair when based on x-rays and moderate when other imaging is included [261].

MRI: MRI is the modality of choice for patients suspected of soft tissue or intra-articular pathology, given its superior sensitivity and specificity [111]. Conventional MRI is effective at identifying osteochondral injuries, musculotendinous pathologies, and inflammation [111]. Magnetic resonance arthrography (MRA) is more appropriate to determine injuries to the labrochondral structures and the ligamentum teres and identify the presence of loose bodies and synovial chondromatosis [111]. The utility of MRA in the accurate detection and staging of articular cartilage lesions is reduced, with sensitivity reported to be less than 50% compared with arthroscopic findings [111]. Recent advances in MRI imaging techniques, such as delayed gadolinium-enhanced MR imaging and T2* mapping, allow for a more in-depth analysis of the structure of articular cartilage [111]. These techniques were effective at detecting early changes to the articular cartilage surfaces of patients with hip dysplasia and femoroacetabular impingement [111].

The anatomy of the proximal femur as well as the version of the acetabulum and femur may be assessed using MRI or magnetic resonance arthrography [24]. Sensitivity to acetabular rim chondral lesions is limited in MRI or magnetic resonance arthrography [24]. In patients with FAIS, both MRI and MRA have excellent reliability for quantifying hip capsular thickness [240]. Significant agreement of angular measurements for hip morphology exists between Zero Echo Time (ZTE) MRI and CT imaging [251]. Preoperative MRI did not alter indications for primary hip arthroscopy in patients aged 40 years and younger with a history, physical examination findings, and radiographs concordant with FAIS [226]. Preoperative MRI for patients with FAIS aged 40 or under undergoing primary hip arthroscopy provides little to no actionable clinical information with respect to the labrum or cartilage [262]. Furthermore, preoperative MRI for this demographic may negatively impact outcomes by delaying access to care unnecessarily by at least two weeks [262]. MRI is useful to diagnose or rule out non-FAI pathology, ascertain labral pathology, and outline hip alignment [235]. Clinicians must 'treat the patient, not the MRI' regarding the diagnosis of impingement [88].

CT: CT scans are effective for examining cortical and cancellous bone and can be used to create three-dimensional reconstructions of the hip for use in surgical planning [111]. Measurements of femoral head coverage and acetabular and femoral impingement can also be performed reliably using CT images [111]. Computed tomography scans allow for accurate definition of deformities and are particularly helpful in revision hip arthroscopy [234]. Multidirectional CT arthrography demonstrated promising diagnostic strength for hip lesions such as labral tears and chondral defects [242].

Ultrasonography: Ultrasonography provides real-time dynamic assessment of the hip and is useful in diagnosing soft-tissue abnormalities about the hip joint [101]. It is particularly useful in providing real-time guidance during diagnostic and therapeutic procedures [101]. Although ultrasonography is a valuable tool to examine pediatric hip conditions, its utility in evaluating the adult hip is limited [111]. Ultrasonography can be an effective modality to identify musculotendinous disruptions, effusions associated with intra-articular pathology, or inflammatory conditions, such as bursitis [111]. It is also being increasingly used for targeted injections into muscles, tendons, or intra-articularly around the hip [111].

Other Considerations: The presence of apparently abnormal imaging findings in asymptomatic patients is well-known; while preventive treatment cannot be justified for labral tears in the hip, patients should be informed that there is a 21% risk of developing symptoms [67]. Most patients with unilateral symptomatic FAI and radiographic diagnosis of bilateral FAI became symptomatic relatively quickly and most of them underwent subsequent surgical intervention in the contralateral hip [250]. Small changes in acetabular rim morphology on the order of 0.5 mm may be the difference between symptomatic FAIS and the unaffected hip [254]. Studies of patients undergoing hip arthroscopy for femoroacetabular impingement syndrome demonstrated increased radiographic progression of hip osteoarthritis over time [255]. These data suggest that symptomatic hips with radiographic features of cam FAI have improved clinical outcomes and lower failure rates when the structural impingement abnormality is surgically corrected [259].

Treatment

Non-Operative

Physical therapy constitutes the first-line treatment for hip microinstability, prioritizing the strengthening of dynamic stabilizers [25]. Nonsurgical management of hip hypermobility or microinstability targets periarticular musculature, specifically the iliopsoas, gluteals, adductors, rotators, and core musculature [26]. Strengthening the abductor and external rotator groups is particularly important for maintaining a level pelvis and preventing adduction and internal rotation during single-leg stance [26]. Neuromuscular reeducation, including proprioceptive and perturbation training, may benefit individuals with joint hypermobility [26]. Flexibility exercises are prescribed with caution only after end-feels have been assessed and are discouraged in patients with excessive range of motion [26]. For hip dysplasia, a trial of conservative management involving anti-inflammatory medications, activity modification, physical therapy, and intra-articular injections should precede surgical consideration [140]. Nonoperative treatment remains the first line for most femoroacetabular impingement (FAI) patients and should not be abandoned for early surgery [214]. Hip arthroscopy is a viable option only after failure to improve following a full course of physical therapy is established [214]. A four-stage conservative program involving anti-inflammatories, rest, guided stretching, and avoidance of provocative hip motions led to significantly improved patient-reported outcomes in a small cohort [191]. There is no agreed-upon conservative care protocol for FAI, with review literature promoting initial nonoperative treatment without established intervention types or duration [191]. Hyaluronic acid injections confer reliable short-term improvements in hip pain and function for symptomatic FAI, though intermediate- and long-term benefits remain undemonstrated [202]. In a meta-analysis of randomized controlled trials, hip arthroscopy was statistically superior to conservative treatment in both long-term and short-term effects [227]. Hip-related quality of life improved by clinically meaningful amounts in both surgery and physical therapy groups in a randomized controlled trial for FAI [193]. No evidence exists on outcomes following non-operative management of FAI with concomitant Tönnis Grade 2 or more hip osteoarthritis [215]. Targeted rehabilitation for FAI should integrate hip-centric and core stabilization exercises, though longitudinal studies are needed to validate therapeutic efficacy [212].

Operative

Indications: Hip arthroscopy is a successful treatment for symptomatic FAI in cases where dysplasia is present, demonstrating low complication rates and a high survivorship rate of 91% at minimum 10-year follow-up [42]. Durable outcomes exceeding 9 years with low revision rates can be expected after hip arthroscopic surgery involving labral preservation and careful attention to capsular closure in patients with borderline dysplasia [17]. Borderline hip dysplasia is not associated with significant differences in hip survivorship or patient-reported outcomes after primary hip arthroscopy for FAI syndrome at minimum 10-year follow-up [43]. Concomitant hip arthroscopy and periacetabular osteotomy (PAO) appears to be a safe and effective procedure with favorable mid-term outcomes that are durable compared to short-term outcomes [21]. Early functional improvements after hip arthroscopy, assessed by 6-month minimal clinically important difference (MCID), predicted clinically meaningful outcomes at 5-year follow-up [77]. Hip arthroscopy for management of FAI and labral tears in patients aged less than 50 demonstrates favorable and safe mid-term outcomes [205]. Age over 40 years should not be considered a contraindication to arthroscopic acetabular labral repair [194]. When surgery is indicated, age 40 years should not be considered an independent contraindication to arthroscopic acetabular labral repair [169]. Surgeons should proceed with caution in patients at least 50 years of age undergoing hip arthroscopy for FAI, requiring careful evaluation of symptoms, hip disease, and expectations [41]. The indication for surgery should be established cautiously when degenerative changes are present [186]. Patients with FAI syndrome and concomitant hip osteoarthritis of Tönnis grade 2 or greater benefit from operative management rather than nonoperative management if they are younger and/or have a normal body mass index [192]. Patients with FAI syndrome and concomitant hip osteoarthritis of Tönnis grade 3 are poor candidates for hip preservation surgery [192]. In a small sample, simultaneous bilateral hip arthroscopy is safe and effective, resulting in similar improvements in patient-reported outcomes at 1-year follow-up compared with staged bilateral procedures [200]. Hip arthroscopy for the treatment of FAI syndrome in competitive athletes and nonathletes produced clinically meaningful outcomes in both patient groups [225]. A positive response to preoperative intra-articular anesthetic injection suggests favorable outcomes after hip arthroscopy in patients with FAI syndrome, with positive responders achieving higher outcome scores and MCID achievement rates [211]. There is a severe lack of evidence on the athlete characteristics and clinical course of nonreturning athletes after hip arthroscopy for FAI syndrome, and the rate of subsequent hip procedures is unknown [37]. Preoperative predictors of return to high functional status after hip arthroscopy for FAI include both modifiable and non-modifiable factors [206].

Surgical Approach / Technique: Hip capsular preservation and closure should remain universal, particularly for patients with specific phenotypes requiring maximum surgical stability, as projected benefits outweigh risks [4]. The management of the hip capsule is critical and must allow for improved exposure without compromising stability and kinematics of the hip [8]. Short-term outcome studies suggest that capsular closure is safe and effective in nonarthritic patients undergoing hip arthroscopic procedures and may yield superior outcomes compared with unrepaired capsulotomy [231]. Data from a large sample confirm that hip microinstability can be successfully treated with plication, particularly in reducing unwanted symptoms and improving overall quality of life [78]. During hip arthroscopy for microinstability, it is important to determine whether the labral-femoral head seal is reestablished following labral repair by visualization on dynamic examination [157]. If the hip capsule is felt to be loose during arthroscopic examination, thermal capsulorrhaphy may help shrink redundancy or absorbable sutures may be used to plicate the capsule [157]. A standard arthroscopic hip capsulotomy involves a 2.5-cm capsulotomy performed parallel to the acetabular labrum and located 10 mm distal from the labral tip [157]. At least 50% of the iliofemoral ligament (IFL) is damaged when performing subspine trimming using a transverse interportal capsulotomy [157]. Care should be taken when performing an intraportal capsulotomy to preserve as much of the IFL as possible [157]. The capsule should be repaired following arthroscopy to avoid instability due to the capsulotomy [157]. In patients who previously underwent hip arthroscopy and present with symptomatic defects on the hip capsule, a reconstruction procedure should be considered to restore integrity, prevent adhesions, and improve stability [157]. Capsular reconstruction is a technically demanding procedure that requires advanced skills in hip arthroscopy and necessitates prolonged physical therapy to restore hip function [157]. Current evidence supports ligamentum teres (LT) reconstruction predominantly for patients experiencing refractory instability following previous hip preservation procedures [75]. An iliofemoral ligament-preserving skip capsulotomy technique may reduce the risk of postoperative instability and pain, particularly in patients with borderline hip stability [233].

Other Considerations: A reconstructive acetabular osteotomy is the treatment of choice for symptomatic hip with moderate dysplasia (lateral center-edge angle <15°) [31]. The Bernese periacetabular osteotomy (PAO) has been popularized for acetabular reorientation and is now a mainstay of surgical treatment for hip dysplasia [31]. PAO is increasingly combined with hip arthroscopy in a single setting when labral pathology is present, with hip arthroscopy performed first [31]. Advantages of the PAO include a single surgical incision, preservation of blood supply to the acetabulum, maintenance of posterior column integrity, and the ability to perform major multidimensional precise acetabular correction [31]. Disadvantages of the PAO include anterior overcorrection producing acetabular retroversion and associated secondary FAI, intra-articular fracture, and neurovascular injury [31]. Reported survival for PAO is 60% at 20-year follow-up [31]. Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) assessment of glycosaminoglycan (GAG) content is predictive of outcome after PAO, with low GAG content associated with increased risk of failure [31]. Hip arthroscopy for borderline hip dysplasia has a role with narrow indications, particularly in revision settings where the root cause of failure must be identified; instability-driven symptoms primarily indicate periacetabular osteotomy [74]. Concomitant procedures represent a powerful solution for the treatment of severe hip dysplasia and intra-articular pathologies resulting from instability or combined FAI syndrome [87]. Hip arthrodesis is uncommonly used but can be used to treat advanced hip degeneration, often posttraumatic, in a very specific patient population [8]. Indications for hip arthrodesis include age younger than 30 years, high activity level, severe pain and stiffness, and normal adjacent joints [8]. Contraindications for hip arthrodesis include disease of the adjacent joints (lumbar spine, contralateral hip, ipsilateral knee), major limb-length discrepancy (>2.0 cm), and active infection [8]. The preferred position for hip arthrodesis is 25° to 30° of hip flexion, 0° to 5° of adduction, and 5° to 10° of external rotation [8]. Hip arthrodesis achieves lasting pain relief and satisfactory clinical results in most patients [8]. Survivorship of hip arthrodesis can be limited by symptomatic degenerative disease of the adjacent joints, with low back pain and osteoarthritis of the ipsilateral knee being the most common problems [8]. Conversion of hip fusion to total hip arthroplasty is occasionally needed, with good clinical results seen in most patients [8].

Complications

Iatrogenic Instability and Dislocation

Acute iatrogenic dislocation is a reported complication following hip impingement arthroscopic surgery [8]. Hip subluxation may occur after arthroscopic debridement [33], while anterior dislocation can develop in patients with capsular laxity [34]. Arthroscopic surgery performed without correction of underlying dysplasia is associated with poor clinical results due to persistent structural instability [195]. Patients with capsular laxity or surgical compromise of the capsule during exposure face a risk of persistent symptoms from capsular incompetency [195]. Subtle instability may occur postoperatively, potentially contributing to prolonged recovery and negatively influencing the outcome [195].

General Complication Rates and Safety

Persistent structural disease is the most common cause of repeat hip preservation surgery [12]. Inadequate femoral osteochondroplasty resulting in residual FAI has been cited as a leading cause of failure after arthroscopy [222]. Capsular deficiency may be an increasingly common cause for pain after hip arthroscopy [222]. At a minimum of 10-year follow-up, the THR conversion rate was 24.2% (23 patients) following hip arthroscopy for FAI [224]. A second surgical procedure was required in 16 patients (16.8%) in less than 3 years following hip arthroscopy for FAI [224]. The cumulative survival probability 10 years after hip arthroscopy surgery was 72.6% [224]. At a mean of 10 years postoperatively, 91% of hips remain preserved following FAI surgery [82]. Patients undergoing primary hip arthroscopy with capsular repair experienced a high survivorship rate of 91% at a minimum 10-year follow-up [83]. Patients undergoing primary hip arthroscopy with capsular repair experienced a high rate of survivorship of 91.0% at minimum 10-year follow-up [85]. Hip arthroscopy for symptomatic femoroacetabular impingement in cases where dysplasia is present demonstrates low complication rates and a high survivorship rate of 91% at minimum 10-year follow-up [42]. The outcomes reported in the literature after hip arthroscopy with microfracture for chondral defects are generally positive, with a very low percentage of patients requiring further surgery or experiencing complications [40].

Specific Surgical Complications

Femoral neck fracture is a reported complication after arthroscopic management of femoroacetabular impingement [12]. Abdominal compartment syndrome is a reported complication after hip arthroscopy [12]. Venous thromboembolic disease is a reported complication following hip arthroscopy [12]. Fatal pulmonary embolism is a reported complication in a polytraumatized patient following hip arthroscopy [12]. Symptoms of nerve dysfunction after hip arthroscopy are an under-reported complication [12]. Surgical hip dislocation carries risks including relatively long rehabilitation due to greater trochanter osteotomy, risk of intraarticular adhesions, trochanteric pain attributable to screws, and a long scar lateral to the hip [218]. Hip arthroscopy has inherent limitations including restricted access to the acetabulum and posterior aspects of the hip, and risk of under- or overcorrection of FAI pathomorphology [218].

Periprosthetic Instability (Total Hip Arthroplasty Context)

Dislocation is the most common reason for revision surgery after arthroplasty within 2 years of injury [198]. The dislocation rate following total hip arthroplasty has declined steadily, with recent randomized trials reporting an incidence of 8% [198]. Use of a posterior approach increases the dislocation rate by a relative risk of 1.3 compared to other approaches [198]. High abduction combined with high anteversion results in anterior instability with hip extension [32]. Low abduction combined with low anteversion results in posterior instability with hip flexion [32]. Decreased femoral offset and inadequate leg length restoration can result in femoral neck impingement against the pelvis or acetabular implant [32]. Decreased femoral offset and inadequate leg length restoration can result in decreased abductor mechanism efficiency due to reduced moment arm [32]. Female sex is associated with an increased dislocation rate in total hip arthroplasty [32]. Osteonecrosis and femoral neck fractures are associated with an increased dislocation rate in total hip arthroplasty [32]. Spinal fusion or limited lumbar spine mobility is associated with an increased dislocation risk in total hip arthroplasty [32]. Revision total hip arthroplasty carries an increased dislocation risk compared to primary total hip arthroplasty [32]. Increased femoral head size (>36 mm) has been associated with a clinical, substantial reduction in dislocation rates [32]. Increased femoral head size (>36 mm) has been associated with an increased incidence of groin pain [32]. Increased femoral head size (>36 mm) has been associated with higher polyethylene wear rates among younger and more active patients [32]. Increased femoral head size (>36 mm) has been associated with corrosion and loosening of the head-neck junction [32]. Parkinson's disease is associated with an increased risk of dislocation following hip arthroplasty [198].

Pediatric and Neuromuscular Complications

A retrospective case-control series reported a 65% complication rate following bony hip surgery in children with cerebral palsy [197]. In the same series, 26% of patients experienced multiple complications following bony hip surgery for cerebral palsy [197]. Only 15% of complications following bony hip surgery for cerebral palsy required return-to-OR [197]. An additional 2% of complications following bony hip surgery for cerebral palsy were life-threatening (Clavien-Dindo III-IV) [197]. Complication rates for salvage procedures in late-presenting painful hip dislocations in cerebral palsy patients were 24% for femoral head resection, 33.3% for valgus-producing osteotomy, 35.3% for total hip arthroplasty, and 28.6% for shoulder prosthetic interposition [197]. The complication rate for hip arthrodesis in this population was reported as 106.3% [197].

Recovery

Survivorship and Long-Term Outcomes: At a mean of 10 years postoperatively, 91% of hips remain preserved following femoroacetabular impingement surgery [82]. Concomitant hip arthroscopy and PAO appears to be a safe and effective procedure with favorable mid-term outcomes that are durable compared to the short-term [21]. These findings support the use of hip arthroscopy as a durable and effective treatment for femoroacetabular impingement syndrome in patients with borderline hip dysplasia [43]. Bilateral hip arthroscopy achieved long-term outcomes and reoperation-free survivorship comparable to those of unilateral hip arthroscopy [210], and patients experience significant clinical benefit in both hips after staged bilateral hip arthroscopy [266].

Outcome Prediction and Trajectories: Early functional improvements after hip arthroscopy, assessed by 6-month MCID, predicted clinically meaningful outcomes at 5-year follow-up [77]. Similarly, early improvements in PROMs following hip arthroscopy, assessed by 6-month MCID, predicted clinically meaningful outcomes at 5-year follow-up [209]. Patients who experienced greater improvement in the first year after hip arthroscopy had superior 10-year outcome scores, fewer complications, and lower rates of reoperation compared with those who experienced minimal improvement in the same period [94]. Although short-term trajectories were similar between groups up to 12-weeks postoperative, long-term trajectories were less favourable for individuals with moderate-to-severe hip osteoarthritis [264]. At long-term follow-up, HSS patients with concomitant lumbar spinal disease demonstrated significant improvements in hip function following HA for FAIS, but with lower mHHS and NAHS scores and decreased rates of MCID achievement compared to controls [196].

Factors Influencing Recovery: Patients with a preoperative duration of FAIS-associated symptoms of 2 or more years prior to hip arthroscopy experience inferior outcomes and a lower frequency of clinically significant outcome improvement than patients with a shorter duration of symptoms at medium-to long-term follow-up [258]. In an adolescent cohort of symptomatic FAI patients who underwent hip arthroscopy, there is no difference in PRO measures when analyzing symptom duration by arbitrary time intervals or as a continuous variable [263]. Younger age and shorter duration of symptoms at time of surgery correlated with greater length of career and years played after hip arthroscopy in professional hockey players [269]. Female patients across a wide range of ages, BMIs, and symptom durations experience satisfactory 5-year outcomes following primary hip arthroscopy, but higher BMI is associated with reduced improvement in patient-reported outcomes [270]. There was no significant difference in Hip-RSI in patients with a history of anxiety and/or depression at any timepoint following hip arthroscopy for femoroacetabular impingement [267].

Contralateral Hip Progression: At a mean follow-up of 7.1 years, significant symptoms in the contralateral hip of patients with FAI were present in approximately 50% of patients [93]. At a mean follow-up of 6.7 years, significant symptoms in the contralateral hip of patients with FAI are present in 50.7% of patients, while 49.3% remain asymptomatic or minimally symptomatic [95]. A prospective longitudinal cohort study demonstrated a 51% rate of significant symptomatic development in the contralateral FAI hip at minimum 10-year follow-up, with 26% of patients experiencing symptoms at baseline [265]. The incidence of a symptomatic labral tear in asymptomatic contralateral hips with femoroacetabular impingement was 9% during 2 years of followup [89].

Return to Sport and Athlete Outcomes: There is a severe lack of evidence on the athlete characteristics and clinical course of the nonreturning athletes, and the rate of subsequent hip procedures is unknown [37].

Key Evidence

• [L4] High rates of FAI morphologic characteristics are present in patients with hip instability. [1] (10.1016/j.arthro.2015.07.021)
• [L5] Evaluation of the patient with recurrent hip instability should be approached systematically with a thorough history and physical examination, along with a focused and targeted radiographic evaluation as indicated. [2] (10.1016/j.arth.2018.01.052)
• [L4] Hips at greatest risk of failure have advanced arthrosis or a combination of impingement and instability preoperatively. [3] (10.1097/01.blo.0000150307.75238.b9)
• [L5] Hip capsular preservation and closure should remain universal, particularly for patients with specific phenotypes requiring maximum surgical stability, as projected benefits outweigh risks and evidence suggests more robust clinical outcomes. [4] (10.1016/j.arthro.2024.03.015)
• [L5] Hip dysplasia is a pathoanatomic osseous morphology associated with hip instability that may, in part, be due to hip capsular thickness. [5] (10.1016/j.arthro.2024.07.012)
• [L4] Additional studies are needed to determine protective or adaptive factors in patients with abnormal anatomy who do not develop early OA and to determine whether joint preserving hip surgery extends the life of the native hip joint. [6] (10.5435/jaaos-d-16-00532)
• [L4] Patient-reported outcome measures and diagnostic imaging are the most frequently reported outcomes, while measures of hip strength and range of motion are underreported, and current surgical outcomes are limited to mid-term follow-up time frames with inconsistent reporting. [7] (10.1016/j.arthro.2017.11.037)
• [L5] The management of the capsule is critical and must allow for improved exposure without compromising stability and kinematics of the hip. [8] (10.1016/j.arthro.2011.08.288)
• [Paper] This article describes a comprehensive approach to interpretation of magnetic resonance examination of the hip, including optimal sequences and planes for identifying key pathology and quantifying bony morphology. [10] (10.1016/j.eats.2017.06.062)
• [L4] The study showed a significant association between acetabular labral tears and structural abnormalities of the hip, with 87% of patients having at least one abnormality detectable on conventional radiographs. [11] (10.1097/01.blo.0000136903.01368.20)
• [Paper] A thorough evaluation of the hip must include a comprehensive medical and surgical history focused on the hip joint, surrounding soft tissues, and associated structures, followed by a physical examination in multiple positions and gait assessment to distinguish between intra-articular and extra-articular contributors to hip pain. [13] (10.1016/j.eats.2017.03.027)
• [L5] The frequency of complications reported for hip arthroscopy for all indications is generally less than 1.5%, suggesting the procedure is safe. [15] (10.1007/s11999-008-0618-4)
• [L5] The shelf acetabuloplasty technique offers limited invasiveness while allowing the comprehensive management of hip instability related to moderate dysplasia. [16] (10.1016/j.otsr.2019.01.004)
• [L3] Durable outcomes (>9 years) with low revision rates can be expected after hip arthroscopic surgery with an approach that involves labral preservation where possible and careful attention to capsular closure in patients with borderline dysplasia. [17] (10.1177/03635465231161348)
• [L4] Open surgical hip dislocation can benefit patients with complex pathology who are not candidates for hip arthroscopy, demonstrating high survivorship and improvements in patient-reported outcomes. [18] (10.1097/corr.0000000000003118)
• [L5] [19] (10.1177/0363546513476281)
• [L3] Long-term outcomes after isolated hip arthroscopy in borderline dysplasia patients are favorable with low revision rates and equivalent outcomes to a nondysplastic cohort. [20] (10.1177/2325967121s00561)
• [L4] Concomitant hip arthroscopy and PAO appears to be a safe and effective procedure with favorable mid-term outcomes that are durable compared to the short-term. [21] (10.1016/j.arthro.2018.10.143)
• [L5] Management of hip microinstability focuses on strengthening the dynamic stabilizers of the hip through focused physical therapy. [25] (10.1016/j.arthro.2021.12.001)
• [Paper] FAI syndrome is defined as a motion-related clinical disorder of the hip with a triad of symptoms, clinical signs and imaging findings. [28] (10.1136/bjsports-2016-096743)
• [L5] [29] (10.5435/00124635-201300001-00004)
• [L4] As there is a high percentage of overlapping (identical or similar) questions between the most commonly used hip-specific PROs for FAIS, multiple tests may be appropriate for use. [30] (10.1177/0363546521999403)
• [L4] Hip-combined rotational morphology has little short-term impact on clinical outcomes after hip arthroscopy in FAIS patients. [33] (10.1002/arj.70330)
• [L5] The editorial congratulates the authors for providing cutoff values for clinically important improvement and functional problems 1 year after hip arthroscopy, and calls for future research to identify causes of persistent pain and decreased function. [34] (10.1016/j.arthro.2019.03.014)
• [L4] Some patients who suffer instability after hip arthroscopy for FAI do not show improved outcomes after surgery. [35] (10.1016/j.arthro.2013.09.050)
• [L3] For determining the presence of a crossover sign, advanced 3D CT-generated hip models improve inter- and intra-observer agreement. [36] (10.1007/s00167-014-3315-8)
• [L1] There is a severe lack of evidence on the athlete characteristics and clinical course of the nonreturning athletes, and the rate of subsequent hip procedures is unknown. [37] (10.1177/0363546520956292)
• [L4] Hip arthroscopy in patients with generalized ligamentous laxity yields favorable outcomes and survivorship at 5-year minimum follow-up comparable to patients without generalized ligamentous laxity. [39] (10.1002/arj.70078)
• [L4] The outcomes reported in the literature after hip arthroscopy with microfracture for chondral defects are, in general, positive, with a very low percentage of patients requiring further surgery or experiencing complications. [40] (10.1016/j.arthro.2015.06.041)
• [L5] Careful evaluation of symptoms, hip disease, and expectations is needed before proceeding, and surgeons should proceed with caution in patients at least 50 years of age. [41] (10.1016/j.arthro.2019.07.002)
• [L4] Hip arthroscopy for symptomatic femoroacetabular impingement is a successful treatment in cases where dysplasia is present, demonstrating low complication rates, comparable outcomes to nondysplastic cases, and a high survivorship rate of 91% at minimum 10-year follow-up. [42] (10.1016/j.arthro.2024.08.022)
• [L4] These findings support the use of hip arthroscopy as a durable and effective treatment for femoroacetabular impingement syndrome in this population. [43] (10.1177/03635465251405728)
• [L4] [48] (10.1177/03635465221075349)
• [L5] [51] (10.1016/j.arthro.2024.06.003)
• [L3] A clinical diagnosis of hip osteoarthritis was found in approximately 22% of young patients undergoing hip arthroscopy within 2 years. [54] (10.1186/s12891-019-2646-5)
• [L2] Radiographic evidence of FAI is common in active patients with hip complaints. [57] (10.1007/s11999-010-1233-8)
• [L3] An isolated assessment of the LCEA is an oversimplistic approach that may jeopardize appropriate classification and may provide insufficient data to guide the treatment of hips with additional features of dysplasia and instability. [61] (10.1177/0363546518810731)
• [L3] The overall prevalence of radiographic findings consistent with FAI in young patients presenting with hip pain was 60.5%. [62] (10.1177/0363546519896355)
• [L5] Both acetabular and femoral morphology are critical to understanding femoroacetabular impingement and developing patient-specific treatments, as the complex interplay of versions influences outcomes and the presence of asymptomatic lesions. [63] (10.1016/j.arthro.2021.09.033)
• [L4] Pathologic thickening of the hip capsule may contribute to restricted hip mobility on clinical examination. [65] (10.1007/s00167-018-4915-5)
• [L5] The presence of apparently abnormal imaging findings in asymptomatic patients is well-known, and while preventive treatment cannot be justified for labral tears in the hip, patients should be informed that there is a 21% risk of developing symptoms. [67] (10.1097/corr.0000000000000606)
• [L3] These findings demonstrate that the femoral head translates the same under bodyweight loading as previously observed during supine exam, showing the inherent stability of the hip with no history of surgery or symptomatic pathology. [68] (10.1097/corr.0000000000002144)
• [L3] Approximately one in four patients with FAI presents with symptoms in the contralateral hip, and 16% of initially asymptomatic contralateral hips will develop symptoms during the next several years. [69] (10.1177/2325967116s00176)
• [L5] [70] (10.1016/j.arthro.2022.04.007)
• [L5] Sensitivity, specificity, and intraobserver and interobserver observational consistency for femoroacetabular impingement radiographic diagnosis require confirmation; until radiologic criteria are confirmed, hip arthroscopic surgeons must rely on expert clinical examination. [72] (10.1016/j.arthro.2015.04.104)
• [L3] In certain cases, hip arthroscopy can be cost-effective given a long enough duration of benefit and appropriate patient selection. [73] (10.1177/2325967120987538)
• [L5] Hip arthroscopy for borderline hip dysplasia has a role with narrow indications, particularly in revision settings where the root cause of failure must be identified; instability-driven symptoms primarily indicate periacetabular osteotomy. [74] (10.1016/j.arthro.2024.06.026)
• [L4] Current evidence supports for LT reconstruction predominantly for patients experiencing refractory instability following previous hip preservation procedures. [75] (10.1016/j.arthro.2021.01.022)
• [L4] Hip arthroscopy for FAI results in increased patient-reported outcome measures at interval follow-up, with most patients reaching critical thresholds of minimal and satisfactory clinical improvement. [76] (10.1016/j.arthro.2019.06.020)
• [L3] Early functional improvements after hip arthroscopy, assessed by 6-month MCID, predicted clinically meaningful outcomes at 5-year follow-up. [77] (10.1177/23259671251352195)
• [L3] Data from this large sample confirm that hip microinstability can be successfully treated with plication, particularly in reducing unwanted symptoms and improving overall quality of life. [78] (10.1016/j.jisako.2023.03.057)
• [L1] Both hip arthroscopy and open surgical hip dislocation showed excellent and equivalent hip survival rates at medium-term follow-up with hip-specific outcome measures, demonstrating equivalence between groups. [79] (10.1177/0363546515587719)
• [L4] Periacetabular osteotomy used as a salvage procedure for patients with hip instability recalcitrant to prior arthroscopy demonstrated substantial improvement in patient-reported outcome measures and radiographic correction of acetabular coverage. [80] (10.2106/jbjs.20.00087)
• [L2] At a mean of 10 years postoperatively, 91% of hips remain preserved. [82] (10.2106/jbjs.25.01341)
• [L3] Patients undergoing primary hip arthroscopy with capsular repair experienced a high survivorship rate of 91% at a minimum 10-year follow-up. [83] (10.1177/03635465241248603)
• [L3] Patients undergoing primary hip arthroscopy with capsular repair experienced a high rate of survivorship of 91.0% at minimum 10-year follow-up. [85] (10.1177/2325967123s00008)
• [L3] Acetabular chondral flap type visualized during hip arthroscopy correlates with radiographic markers of hip impingement and hip instability. [86] (10.1177/0363546519871065)
• [L5] Concomitant procedures represent a powerful solution for the treatment of severe hip dysplasia and intra-articular pathologies resulting from instability or combined FAIS. [87] (10.1016/j.arthro.2024.10.023)
• [L5] The exact definition of 'impingement' eludes the current literature, and while dynamic MRI has potential to better define hip impingement, it is not yet optimized for widespread clinical use; clinicians must 'treat the patient, not the MRI.' [88] (10.1016/j.arthro.2019.05.009)
• [L4] The incidence of a symptomatic labral tear in these asymptomatic hips was 9% during 2 years of followup. [89] (10.1097/corr.0000000000000567)
• [L5] The three primary factors involved in preservation of the hip joint include femoroacetabular impingement, hip dysplasia/instability, and femoral torsion abnormalities. [90] (10.5435/jaaos-d-24-00340)
• [L2] At a mean follow-up of 7.1 years, significant symptoms in the contralateral hip of patients with FAI were present in approximately 50% of patients. [93] (10.1177/03635465221119509)
• [L3] Patients who experienced greater improvement in the first year after hip arthroscopy had superior 10-year outcome scores, fewer complications, and lower rates of reoperation compared with those who experienced minimal improvement in the same period. [94] (10.1177/03635465251342119)
• [L2] At a mean follow-up of 6.7 years, significant symptoms in the contralateral hip of patients with FAI are present in 50.7% of patients, while 49.3% remain asymptomatic or minimally symptomatic. [95] (10.1177/2325967121s00278)
• [L3] [118] (10.1177/23259671261434943)
• [L5] Despite simulating lower degrees of hip flexion and internal rotation, increased stress and a shift in contact location were observed in the simulated models of FAI. [122] (10.1016/j.arthro.2017.03.018)
• [L5] Individual and postural variations in physiologic pelvic tilt affect joint contact pressure in the hip. [126] (10.1097/corr.0000000000001737)
• [L4] The clinical impingement sign is challenged as a specific diagnostic test, and the study emphasizes the early nature of hip pathology in athletes. [129] (10.1016/j.otsr.2010.09.005)
• [L4] Increased cam morphology remained a significant contributor to reduced internal rotation but did not affect hip flexion. [130] (10.1016/j.arthro.2020.02.044)
• [L1] Biomechanical evidence supports closure of the capsule after hip arthroscopy to reverse the significant effects of capsulotomy. [134] (10.1016/j.arthro.2021.04.004)
• [L4] Hip strength deficits were common in patients presenting with unilateral symptomatic FAI and occurred most commonly in hip abduction and flexion. [137] (10.1016/j.arthro.2015.04.095)
• [Paper] The puncture capsulotomy technique preserves the native anatomy and biomechanics of the hip joint by leaving the iliofemoral ligament intact, thereby eliminating the risk of gross anterior dislocation and avoiding postoperative range-of-motion restrictions associated with traditional capsulotomy. [143] (10.1016/j.eats.2017.08.036)
• [L3] FAI participants altered their walking kinematics and kinetics, especially during contralateral foot-strike, as a protective mechanism, which resulted in reduced psoas major and iliacus muscle force and anterosuperior hip contact force estimations. [144] (10.1177/0363546518787518)
• [L5] Clinical identification of combined impingement and dysplasia is imperative to potentially improve patient outcomes. [146] (10.1002/arj.70215)
• [L5] The presence of FAI morphology does not necessarily mean that FAI is the primary source of hip pain; other less common causes, such as osteoid osteoma, should be included in the differential diagnosis, especially when atypical clinical and radiological signs are found. [149] (10.1007/s00167-014-2985-6)
• [L5] At 70 and 90 of hip flexion, a combined change in 3D pelvic alignment of 5- (ie, St, axial rotation, and coronal tilt) was more effective in improving hip maximum internal rotation than a 10 change in sagittal tilt only. [150] (10.1177/23259671221123604)
• [L4] Hip impingement in those with FAIS may routinely occur at hip flexion angles below 90° in neutral rotation, with males engaging at higher flexion angles than females. [161] (10.1002/arj.70005)
• [L3] Considering the high prevalence of radiographic hip findings reminiscent of FAI in asymptomatic Asian populations, it will be important to determine whether FAI-related morphologic features are a cause of hip pain when considering surgery in Asian patients. [163] (10.1007/s11999-016-5013-y)
• [L5] The mechanical loading on the acetabular cartilage in cam-type hips is left unchanged regardless of labral size during walking and deep flexion, suggesting similar levels of susceptibility to cartilage damage. [165] (10.1177/2325967124s00154)
• [L5] Clinicians should evaluate for the Beighton score and additional radiographic factors suggestive of instability in patients with combined borderline hip dysplasia and excessive femoral anteversion, as these findings may portend inferior outcomes after arthroscopic treatment in isolation, making open procedures like periacetabular osteotomy a more reliable option for symptomatic hip instability. [166] (10.1016/j.arthro.2022.12.001)
• [L3] Extraarticular FAI is an uncommon source of impingement symptoms, often missed due to prior hip surgery, and seems more common in younger, female patients. [167] (10.1007/s11999-014-4001-3)
• [L2] Acetabular and femoral osseous abnormalities commonly are associated with labral tears, and recognition of these abnormalities is important to optimize surgical treatment of patients with symptomatic labral disease. [168] (10.1097/01.blo.0000181147.86058.74)
• [L1] When surgery is indicated, age 40 years should not be considered an independent contraindication to arthroscopic acetabular labral repair. [169] (10.1177/03635465241263595)
• [L3] Approximately 1 in 4 patients with FAI presents with symptoms in the contralateral hip, and an additional 1 in 4 patients develops significant symptoms in the following 4 years. [172] (10.1177/0363546518786246)
• [L3] Understanding of hip disorder-specific chondral damage patterns may be useful for the development of arthroscopic classification of hip disorders and may lead to the establishment of treatment guidelines. [177] (10.1007/s00167-014-3297-6)
• [L3] No biomechanical differences existed between groups during level walking, yet hamstring and gluteus maximus activation differed when the symptomatic group was compared with the asymptomatic group. [182] (10.1177/2325967118769829)
• [L4] The indication for surgery should be established cautiously when degenerative changes are present. [186] (10.1007/s00402-016-2427-7)
• [L4] [191] (10.1055/s-0038-1676448)
• [L5] [192] (10.1016/j.arthro.2023.12.010)
• [L1] Hip-related QOL improved in both groups by clinically meaningful amounts. [193] (10.1136/bjsports-2025-110986)
• [L1] Thus, age over 40 years should not be considered a contraindication to arthroscopic acetabular labral repair. [194] (10.1177/0363546521990789)
• [L4] [195] (10.5435/jaaos-21-07-s53)
• [L3] At long-term follow-up, HSS patients demonstrated significant improvements in hip function following HA for FAIS, but with lower mHHS and NAHS scores and decreased rates of MCID achievement compared to controls. [196] (10.1177/2325967126s00438)
• [L3] It is recommended to perform routine intraoperative repair of the articular capsule at the end of hip arthroscopy, as this has a positive influence on the functional results at short-term follow-up. [199] (10.1186/s12891-024-07894-0)
• [L3] In a small sample, simultaneous bilateral hip arthroscopy is shown to be safe and effective, resulting in similar improvements in patient-reported outcomes at 1-year follow-up compared with staged bilateral procedures. [200] (10.1016/j.arthro.2016.01.047)
• [Paper] Hyaluronic acid injections appear to confer reliable short-term improvements in hip pain and function for symptomatic FAI, but potential intermediate-term and long-term benefit has not yet been demonstrated. [202] (10.2106/jbjs.rvw.24.00211)
• [L3] Patients 40 years who underwent primary hip arthroscopy with labral repair demonstrated a hip preservation rate of 78%, significant and durable improvement in PROMs, and high rates of satisfaction at a minimum 10-year follow-up. [203] (10.1177/03635465241270291)
• [L3] Arthroscopic management of mild to moderate acetabular dysplasia had inferior good/excellent results and higher failure rates when compared with an FAI cohort; therefore, isolated arthroscopic procedures in this population should be cautiously considered. [204] (10.1177/0363546515613068)
• [L3] Hip arthroscopy for management of femoroacetabular impingement and labral tears in patients aged less than 50 demonstrates favorable and safe mid-term outcomes. [205] (10.5435/jaaos-d-17-00258)
• [L3] There are both modifiable and non-modifiable pre-operative factors that have the potential to predict a return to high functional status after hip arthroscopy for FAI. [206] (10.1177/2325967118s00070)
• [L3] Early improvements in PROMs following hip arthroscopy, assessed by 6-month MCID, predicted clinically meaningful outcomes at 5-year follow-up. [209] (10.1177/2325967125s00193)
• [L3] Bilateral hip arthroscopy achieved long-term outcomes and reoperation-free survivorship comparable to those of unilateral hip arthroscopy. [210] (10.1177/03635465251412678)
• [L2] Three of the 4 studies showed significant associations between positive injection response and superior postoperative outcomes, with positive responders achieving higher Hip Outcome Score Activities of Daily Living, Hip Outcome Score-Sports, Nonarthritic Hip Score, and Patient-Reported Outcome Measure Information System scores (P = .003-0.045) and higher minimum clinically important difference/patient acceptable symptomatic state achievement rates. [211] (10.1002/arj.70477)
• [L1] Targeted rehabilitation should integrate hip-centric and core stabilization exercises, but longitudinal studies are needed to validate therapeutic efficacy. [212] (10.1186/s13018-025-06135-x)
• [L5] Nonoperative treatment remains the first line of treatment for most FAI patients and should not be abandoned in favor of early surgery; hip arthroscopy is an appropriate viable option only after failure to improve after a full course of physical therapy is established. [214] (10.1016/j.arthro.2023.05.009)
• [L4] No evidence exists on outcomes following non-operative management of FAI with concomitant Tönnis Grade 2 or more OA of the hip. [215] (10.1007/s00167-022-07274-y)
• [L4] [218] (10.1007/s11999-016-5115-6)
• [L3] Classifying acetabular dysplasia into 3 groups based on the plane of instability could optimize the planning of PAO by giving a better understanding of the 3-dimensional deformity. [221] (10.1177/0363546521992108)
• [L5] [222] (10.5435/jaaos-d-16-00928)
• [L4] [224] (10.1016/j.arthro.2024.08.012)
• [L3] Hip arthroscopy for the treatment of FAIS in competitive athletes and nonathletes produced clinically meaningful outcomes in both patient groups. [225] (10.1177/0363546519885359)
• [L3] Preoperative MRI did not alter indications for primary hip arthroscopy in patients aged 40 years and younger with a history, physical examination findings, and radiographs concordant with FAIS. [226] (10.1177/23259671221144776)
• [L1] In our meta-analysis, hip arthroscopy is statistically superior to conservative treatment in both long-term and short-term effects. [227] (10.1186/s13018-022-03187-1)
• [L2] [228] (10.1097/corr.0000000000001706)
• [L1] Short-term outcome studies suggest that capsular closure is safe and effective in nonarthritic patients undergoing hip arthroscopic procedures and may yield superior outcomes compared with unrepaired capsulotomy. [231] (10.1016/j.arthro.2017.06.030)
• [L3] A computer-assisted analysis of young adult hip radiographs generally demonstrates substantial to excellent levels of interobserver reliability for most parameters. [232] (10.1177/0363546514542797)
• [L5] This technique may reduce the risk of postoperative instability and pain, particularly in patients with borderline hip stability, and facilitate earlier functional recovery. [233] (10.1016/j.eats.2025.103769)
• [L5] Plain radiographs are key in the initial assessment of patients suspected of femoroacetabular impingement, while computed tomography scans allow for accurate definition of deformities and are particularly helpful in revision hip arthroscopy. [234] (10.1016/j.csm.2016.02.002)
• [L4] In addition, MRI is useful to diagnose or rule out non-FAI pathology, ascertain labral pathology, and outline hip alignment; these methods of preoperative planning are complementary. [235] (10.1016/j.asmr.2021.07.015)
• [L2] In joint-preserving hip surgery, lesions of the ligamentous-fossa-foveolar complex (LFFC) are very common, with 65% of hips showing substantial damage. [237] (10.1097/corr.0000000000003825)
• [L3] [238] (10.1177/03635465241255950)
• [L4] In patients with FAIS, both MRI and MRA have excellent reliability for quantifying hip capsular thickness. [240] (10.1016/j.asmr.2023.100874)
• [L3] Patients with borderline hip dysplasia and radiographic evidence of hip instability, as measured by the FEAR index (≥2), may achieve similar improvement in 2-year outcomes compared to those with radiographically stable hips after arthroscopic treatment of FAIS. [241] (10.1016/j.arthro.2021.10.012)
• [L2] In addition, multidirectional CTA demonstrated promising diagnostic strength for hip lesions such as labral tears and chondral defects. [242] (10.1177/23259671221143459)
• [L4] We concluded cam and pincer hips are distinct pathoanatomic entities. [245] (10.1007/s11999-010-1347-z)
• [L1] [246] (10.1177/0363546517749475)
• [L4] Radiological evidence of symptomatic femoroacetabular impingement was not uncommon in these Japanese patients with hip pain, with cam deformity findings being the most common. [248] (10.1302/0301-620x.96b2.32680)
• [L3] Most patients with unilateral symptomatic FAI and radiographic diagnosis of bilateral FAI became symptomatic relatively quickly and most of them underwent subsequent surgical intervention in the contralateral hip. [250] (10.1097/corr.0000000000000699)
• [L2] Significant agreement of angular measurements for hip morphology exists between ZTE MRI and CT imaging. [251] (10.1177/0363546519878170)
• [L3] A narrow posterior joint space on a False Profile radiograph does not correlate with posterior joint cartilage degeneration in hip preservation patients. [252] (10.1016/j.arthro.2020.07.023)
• [L4] Small changes in acetabular rim morphology on the order of 0.5 mm may be the difference between symptomatic FAIS and the unaffected hip. [254] (10.1016/j.asmr.2019.06.001)
• [L4] Studies of patients undergoing hip arthroscopy for femoroacetabular impingement syndrome demonstrated increased radiographic progression of hip osteoarthritis over time. [255] (10.1177/23259671251326116)
• [L3] Patients with a preoperative duration of FAIS-associated symptoms of 2 or more years prior to hip arthroscopy experience inferior outcomes and a lower frequency of clinically significant outcome improvement than patients with a shorter duration of symptoms at medium-to long-term follow-up. [258] (10.1016/j.arthro.2019.08.032)
• [L3] These data suggest that symptomatic hips with radiographic features of cam FAI have improved clinical outcomes and lower failure rates when the structural impingement abnormality is surgically corrected. [259] (10.1016/j.arth.2008.11.040)
• [L4] Radiographic indicators of FAI are very common among athletes evaluated at the National Football League Scouting Combine subjected to radiographic examination for the clinical suspicion of hip disease. [260] (10.1016/j.arthro.2012.03.005)
• [L3] Our study shows that surgeons experienced in FAI/Dysplasia have higher interrater agreement in making a diagnosis of such hip disorders than other hip surgeons, however, this remains only fair when based on x- rays and moderate when other imaging is included. [261] (10.1016/j.arthro.2013.09.034)
• [L3] Preoperative MRI for patients with FAIS aged 40 or under undergoing primary hip arthroscopy provides little to no actionable clinical information with respect to the labrum or cartilage and may negatively impact outcomes by delaying access to care unnecessarily by at least two weeks. [262] (10.1177/2325967121s00609)
• [L4] In an adolescent cohort of symptomatic FAI patients who underwent hip arthroscopy, there is no difference in PRO measures when analyzing symptom duration by arbitrary time intervals or as a continuous variable. [263] (10.1016/j.arthro.2023.03.028)
• [L3] Although short-term trajectories were similar between groups up to 12-weeks postoperative, long-term trajectories were less favourable for individuals with moderate-to-severe hip osteoarthritis. [264] (10.1016/j.jisako.2025.100478)
• [L2] This prospective longitudinal cohort study demonstrated a 51% rate of significant symptomatic development in the contralateral FAI hip at minimum 10-year follow-up, with 26% of patients experiencing symptoms at baseline. [265] (10.1177/2325967125s00187)
• [L3] Patients experience significant clinical benefit in both hips after staged bilateral hip arthroscopy. [266] (10.1016/j.arthro.2022.10.048)
• [L3] There was no significant difference in Hip-RSI in patients with a history of anxiety and/or depression at any timepoint. [267] (10.1177/2325967124s00194)
• [L4] Younger age and shorter duration of symptoms at time of surgery correlated with greater length of career and years played after hip arthroscopy. [269] (10.1177/0363546516650649)
• [L3] Female patients across a wide range of ages, BMIs, and symptom durations experience satisfactory 5-year outcomes following primary hip arthroscopy, but higher BMI is associated with reduced improvement in patient-reported outcomes. [270] (10.1016/j.arthro.2023.06.035)

See Also

• Femoroacetabular impingement
• Hip arthroscopy
• Periacetabular osteotomy
• Hip osteoarthritis

References

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[61] Mild or Borderline Hip Dysplasia: Are We Characterizing Hips With a Lateral Center-Edge Angle Between 18° and 25° Appropriately?. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518810731

[62] The Prevalence of Radiographic Findings of Structural Hip Deformities for Femoroacetabular Impingement in Patients With Hip Pain. The American Journal of Sports Medicine. 2020. DOI: 10.1177/0363546519896355

[63] Editorial Commentary: Both Femoral Acetabular Anteversion and Retroversion May Contribute to the Effect of Femoroacetabular Impingement: What’s Your Version?. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2021.09.033

[65] Hip capsular thickness correlates with range of motion limitations in femoroacetabular impingement. Knee Surgery, Sports Traumatology, Arthroscopy. 2018. DOI: 10.1007/s00167-018-4915-5

[67] CORR Insights®: Acetabular Labral Tears Are Common in Asymptomatic Contralateral Hips With Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2019. DOI: 10.1097/corr.0000000000000606

[68] Does Femoral Head Translation Vary by Sex and Side in Asymptomatic Hips During a Weightbearing Apprehension Test?. Clinical Orthopaedics & Related Research. 2022. DOI: 10.1097/corr.0000000000002144

[69] The Fate of the Contralateral Hip in Femoroacetabular Impingement. Orthopaedic Journal of Sports Medicine. 2016. DOI: 10.1177/2325967116s00176

[70] Editorial Commentary: Hip Joint Laxity, Microinstability, or Instability Require Precise Definition: No Matter What You Call It, It's Here to Stay!. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2022.04.007

[72] Editorial Commentary: Radiographic Inclusion and Exclusion Diagnostic Criteria for Femoroacetabular Impingement Require Confirmation. Arthroscopy. 2015. DOI: 10.1016/j.arthro.2015.04.104

[73] Cost-Effectiveness of Hip Arthroscopy for Treatment of Femoroacetabular Impingement Syndrome and Labral Tears: A Systematic Review. Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/2325967120987538

[74] Editorial Commentary: Revision Hip Arthroscopy in Patients With Borderline Dysplasia Has a Role: Indications Are Narrow Versus Periacetabular Osteotomy. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.06.026

[75] Ligamentum Teres Reconstruction May Lead to Improvement in Outcomes Following a Secondary Hip Arthroscopy for Symptomatic Microinstability: A Systematic Review. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2021. DOI: 10.1016/j.arthro.2021.01.022

[76] Outcome Trends After Hip Arthroscopy for Femoroacetabular Impingement: When Do Patients Improve?. Arthroscopy. 2019. DOI: 10.1016/j.arthro.2019.06.020

[77] Six-Month Functional Scores Predict 5-Year Achievement of the Minimal Clinically Important Differences After Hip Arthroscopy for Symptomatic Acetabular Labral Tears. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/23259671251352195

[78] Primary Labral Reconstruction Versus Labral Repair In Patients With Femoroacetabular Impingement: An Inverse Propensity Score Weighted Analysis of Patient Reported Outcomes and Subsequent Surgery Risk. Journal of ISAKOS. 2023. DOI: 10.1016/j.jisako.2023.03.057

[79] Arthroscopic Versus Open Treatment of Femoroacetabular Impingement. The American Journal of Sports Medicine. 2015. DOI: 10.1177/0363546515587719

[80] Periacetabular Osteotomy as a Salvage Procedure. Journal of Bone and Joint Surgery. 2020. DOI: 10.2106/jbjs.20.00087

[82] Survivorship of Femoroacetabular Impingement Surgery at Mean 10-Year Follow-up. Journal of Bone and Joint Surgery. 2026. DOI: 10.2106/jbjs.25.01341

[83] Long-term Survivorship and Outcomes of Patients Without Dysplasia Undergoing Capsular Repair During Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241248603

[85] Paper 08: Long Term Survivorship and Outcomes of Patients Undergoing Capsular Repair and Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/2325967123s00008

[86] The “Outside-In” Lesion of Hip Impingement and the “Inside-Out” Lesion of Hip Dysplasia: Two Distinct Patterns of Acetabular Chondral Injury. The American Journal of Sports Medicine. 2019. DOI: 10.1177/0363546519871065

[87] Editorial Commentary: Arthroscopic Treatment of Mild Hip Dysplasia Can Result in Excellent Outcome and Avoid More Invasive Periacetabular Osteotomy. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.10.023

[88] Editorial Commentary: What Exactly Is Impingement—Can Dynamic Magnetic Resonance Imaging “See” Impingement in Femoroacetabular Impingement?. Arthroscopy. 2019. DOI: 10.1016/j.arthro.2019.05.009

[89] Acetabular Labral Tears Are Common in Asymptomatic Contralateral Hips With Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2018. DOI: 10.1097/corr.0000000000000567

[90] The Principles of Hip Joint Preservation. Journal of the American Academy of Orthopaedic Surgeons. 2024. DOI: 10.5435/jaaos-d-24-00340

[93] Factors Associated With Disease Progression in the Contralateral Hip of Patients With Symptomatic Femoroacetabular Impingement: A Minimum 5-Year Analysis. The American Journal of Sports Medicine. 2022. DOI: 10.1177/03635465221119509

[94] One-Year Outcomes Predict 10-Year Outcomes in Patients Undergoing Hip Arthroscopy for Femoroacetabular Impingement. The American Journal of Sports Medicine. 2025. DOI: 10.1177/03635465251342119

[95] Identification of Factors Associated with Disease Progression in the Contralateral Hip of Patients with Symptomatic Femoroacetabular Impingement. (139). Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/2325967121s00278

[96] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > 2. Arthrology > Hip (Fig. 2.49).

[99] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy and Biomechanics, Evaluation, Clinical Examination, and Imaging of the Hip > Osseous and Ligamentous Anatomy.

[100] Aaos Comprehensive Orthopaedic Review 3. Surgical Anatomy of the Hip > IV. Hip Capsule and Ligaments.

[101] Orthopaedic Knowledge Update Sports Medicine 6. Imaging of the Hip > Introduction.

[111] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy and Biomechanics, Evaluation, Clinical Examination, and Imaging of the Hip > Imaging.

[118] Diagnostic Utility of CT-Based Acetabular Sector Angles in Pincer-Type Femoroacetabular Impingement: Limitations and Clinical Integration. Orthopaedic Journal of Sports Medicine. 2026. DOI: 10.1177/23259671261434943

[122] The Influence of Squat Kinematics and Cam Morphology on Acetabular Stress. Arthroscopy. 2017. DOI: 10.1016/j.arthro.2017.03.018

[126] Does Patient-specific Functional Pelvic Tilt Affect Joint Contact Pressure in Hip Dysplasia? A Finite-element Analysis Study. Clinical Orthopaedics & Related Research. 2021. DOI: 10.1097/corr.0000000000001737

[129] Descriptive epidemiology of mechanical hip pathology in adults under 50 years of age. Prospective series of 292 cases: Clinical and radiological aspects and physiopathological review. Orthopaedics & Traumatology: Surgery & Research. 2010. DOI: 10.1016/j.otsr.2010.09.005

[130] The Bipolar Hip: How Acetabular and Femoral Pathomorphology Affects Hip Motion in Femoral Acetabular Impingement Syndrome. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2020. DOI: 10.1016/j.arthro.2020.02.044

[134] Hip Capsular Management in Patients With Femoroacetabular Impingement or Microinstability: A Systematic Review of Biomechanical Studies. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2021. DOI: 10.1016/j.arthro.2021.04.004

[136] Orthopaedic Knowledge Update. Developmental Dysplasia of the Hip* > Adolescent HIP Dysplasia.

[137] Hip Strength Deficits in Patients With Symptomatic Femoroacetabular Impingement and Labral Tears. Arthroscopy. 2015. DOI: 10.1016/j.arthro.2015.04.095

[138] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy and Biomechanics, Evaluation, Clinical Examination, and Imaging of the Hip > Physical Examination.

[140] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Early Degenerative Changes of the Hip > Hip Dysplasia > Treatments.

[143] Puncture Capsulotomy During Hip Arthroscopy for Femoroacetabular Impingement: Preserving Anatomy and Biomechanics. Arthroscopy Techniques. 2017. DOI: 10.1016/j.eats.2017.08.036

[144] Altered Walking and Muscle Patterns Reduce Hip Contact Forces in Individuals With Symptomatic Cam Femoroacetabular Impingement. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518787518

[145] Orthopaedic Knowledge Update Sports Medicine 6. Hip Microinstability > Bony Abnormalities.

[146] The Literature Shows Heterogeneity and Promise for the Role of Hip Arthroscopy Combined With Periacetabular Osteotomy for Dysplastic Patients, But Nuanced Decision Making and Further Research Are Required. Arthroscopy. 2026. DOI: 10.1002/arj.70215

[149] Atypical hip pain: coexistence of femoroacetabular impingement (FAI) and osteoid osteoma. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-2985-6

[150] Effect of 3-Dimensional Versus Single-Plane Changes in Pelvic Dynamics on Range of Motion in Hips With Femoroacetabular Impingement: A Computer Simulation Analysis. Orthopaedic Journal of Sports Medicine. 2022. DOI: 10.1177/23259671221123604

[157] Orthopaedic Knowledge Update Sports Medicine 6. Hip Microinstability > Treatment.

[161] Impingement in Patients With Femoroacetabular Impingement Syndrome Routinely Occurs Below 90° of Hip Flexion. Arthroscopy. 2026. DOI: 10.1002/arj.70005

[163] What is the Prevalence of Radiographic Hip Findings Associated With Femoroacetabular Impingement in Asymptomatic Asian Volunteers?. Clinical Orthopaedics & Related Research. 2016. DOI: 10.1007/s11999-016-5013-y

[165] Poster 185: The Effect of Labrum Size on Cartilage Mechanics in a Patient with Cam-Type Femoroacetabular Impingement Syndrome. Orthopaedic Journal of Sports Medicine. 2024. DOI: 10.1177/2325967124s00154

[166] Editorial Commentary: Evaluate for the Beighton Score and Additional Radiographic Signs of Instability Prior to Proceeding With Hip Arthroscopy in Patients With Combined Borderline Hip Dysplasia and Excessive Femoral Anteversion. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2022.12.001

[167] What Are the Demographic and Radiographic Characteristics of Patients With Symptomatic Extraarticular Femoroacetabular Impingement?. Clinical Orthopaedics & Related Research. 2015. DOI: 10.1007/s11999-014-4001-3

[168] Acetabular and Femoral Radiographic Abnormalities Associated with Labral Tears. Clinical Orthopaedics and Related Research. 2005. DOI: 10.1097/01.blo.0000181147.86058.74

[169] Hip Arthroscopy Versus Physical Therapy for the Treatment of Symptomatic Acetabular Labral Tears in Patients Older Than 40 Years: 24-Month Results From a Randomized Controlled Trial. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241263595

[172] A Prospective Analysis of the Contralateral Hip Among Patients With Femoroacetabular Impingement: What Are the Risk Factors for Disease Progression?. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518786246

[177] Hip morphology influences the pattern of articular cartilage damage. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-3297-6

[178] Orthopaedic Knowledge Update Sports Medicine 6. Hip Microinstability > Soft Tissue > Hip Capsule.

[181] Orthopaedic Knowledge Update Sports Medicine 6. Athletic Hip Injuries > Hip Instability.

[182] Differences in Hip Joint Biomechanics and Muscle Activation in Individuals With Femoroacetabular Impingement Compared With Healthy, Asymptomatic Individuals: Is Level-Ground Gait Analysis Enough?. Orthopaedic Journal of Sports Medicine. 2018. DOI: 10.1177/2325967118769829

[186] Arthroscopic treatment of femoroacetabular impingement shows persistent clinical improvement in the mid-term. Archives of Orthopaedic and Trauma Surgery. 2016. DOI: 10.1007/s00402-016-2427-7

[191] Rehabilitation for Femoroacetabular Impingement: Conservative Care and Postoperative Practice. The Journal of Hip Surgery. 2018. DOI: 10.1055/s-0038-1676448

[192] Clinical Equipoise in the Management of Patients With Femoroacetabular Impingement Syndrome and Concomitant Tönnis Grade 2 Hip Osteoarthritis or Greater: An International Expert‐Panel Delphi Study. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2023.12.010

[193] Physiotherapist-led treatment for femoroacetabular impingement syndrome (the PhysioFIRST study): an assessor-blinded, limited disclosure randomised controlled trial. British Journal of Sports Medicine. 2026. DOI: 10.1136/bjsports-2025-110986

[194] Hip Arthroscopy Versus Physical Therapy for the Treatment of Symptomatic Acetabular Labral Tears in Patients Older Than 40 Years: A Randomized Controlled Trial. The American Journal of Sports Medicine. 2021. DOI: 10.1177/0363546521990789

[195] Overview of Treatment Options, Clinical Results, and Controversies in the Management of Femoroacetabular Impingement. Journal of the American Academy of Orthopaedic Surgeons. 2013. DOI: 10.5435/jaaos-21-07-s53

[196] Poster 136. Patients With Concomitant Lumbar Spinal Disease Have Less Significant Improvement Than Those Without Lumbar Spinal Disease at 10-Year Follow-up Following Hip Arthroscopy for Femoroacetabular Impingement. Orthopaedic Journal of Sports Medicine. 2026. DOI: 10.1177/2325967126s00438

[197] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Neuromuscular Disorders in Children > Cerebral Palsy > Hip Surveillance and Surgery.

[198] Rockwood And Green S Fractures In Adults. 51: Hip Dislocations and Femoral Head Fractures > Prosthesis Dislocation.

[199] A retrospective cohort study: dual cannula combined with modified shoelace continuous capsular closure technique versus nonrepair in hip arthroscopic surgery of femoroacetabular impingement. BMC Musculoskeletal Disorders. 2024. DOI: 10.1186/s12891-024-07894-0

[200] Simultaneous Versus Staged Bilateral Hip Arthroscopy in the Treatment of Femoroacetabular Impingement. Arthroscopy. 2016. DOI: 10.1016/j.arthro.2016.01.047

[202] Femoroacetabular Impingement: Critical Analysis Review of Current Nonoperative Treatments. JBJS Reviews. 2025. DOI: 10.2106/jbjs.rvw.24.00211

[203] Ten-Year Outcomes in Patients Aged 40 Years and Older After Primary Arthroscopic Treatment of Femoroacetabular Impingement With Labral Repair. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241270291

[204] Arthroscopic Management of Dysplastic Hip Deformities. The American Journal of Sports Medicine. 2015. DOI: 10.1177/0363546515613068

[205] Hip Arthroscopy for Femoroacetabular Impingement and Labral Tears in Patients Younger than 50 Years: Minimum Five-year Outcomes, Survivorship, and Risk Factors for Reoperations. Journal of the American Academy of Orthopaedic Surgeons. 2019. DOI: 10.5435/jaaos-d-17-00258

[206] Pre-operative Predictors of Return to High Functional Status after Hip Arthroscopy for Femoroacetabular Impingement at 2-year Minimum Follow-up. Orthopaedic Journal of Sports Medicine. 2018. DOI: 10.1177/2325967118s00070

[209] Poster 88: Six-Month Functional Scores Predict 5-Year Outcomes after Hip Arthroscopy for Symptomatic Acetabular Labral Tears. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/2325967125s00193

[210] Bilateral Hip Arthroscopy Compared with Unilateral Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Analysis of Long-term Outcomes and Procedural Timing. The American Journal of Sports Medicine. 2026. DOI: 10.1177/03635465251412678

[211] Positive Response to Preoperative Intra‐articular Anesthetic Injection Suggests Favorable Outcomes After Hip Arthroscopy in Patients With Femoroacetabular Impingement Syndrome: A Systematic Review. Arthroscopy. 2026. DOI: 10.1002/arj.70477

[212] Hip muscle changes in femoroacetabular impingement: a systematic review and meta-analysis. Journal of Orthopaedic Surgery and Research. 2025. DOI: 10.1186/s13018-025-06135-x

[214] Editorial Commentary: Nonoperative Management Is the First Line of Treatment for Hip Femoroacetabular Impingement in Adolescents: Children Are Not Little Adults!. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2023.05.009

[215] No evidence exists on outcomes of non‐operative management in patients with femoroacetabular impingement and concomitant Tönnis Grade 2 or more hip osteoarthritis: a scoping review. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-07274-y

[218] What Are the Risk Factors for Revision Surgery After Hip Arthroscopy for Femoroacetabular Impingement at 7-year Followup?. Clinical Orthopaedics & Related Research. 2017. DOI: 10.1007/s11999-016-5115-6

[221] Correlation of Patient-Reported Outcomes After Periacetabular Osteotomy With Femoral Head Coverage and Acetabular Orientation: A Single-Center Cohort Study. The American Journal of Sports Medicine. 2021. DOI: 10.1177/0363546521992108

[222] Approach to the Patient With Failed Hip Arthroscopy for Labral Tears and Femoroacetabular Impingement. Journal of the American Academy of Orthopaedic Surgeons. 2020. DOI: 10.5435/jaaos-d-16-00928

[224] High Survival Rate and Satisfaction at More Than 11‐Year Follow‐Up After Hip Arthroscopy for Femoroacetabular Impingement Syndrome: Impact of Preoperative Functional Scores, Osteoarthritis, and Chondrolabral Junction Damage on Failure. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.08.012

[225] Comparing Outcomes of Competitive Athletes Versus Nonathletes Undergoing Hip Arthroscopy for Treatment of Femoroacetabular Impingement Syndrome. The American Journal of Sports Medicine. 2019. DOI: 10.1177/0363546519885359

[226] Evaluating the Need for Preoperative MRI Before Primary Hip Arthroscopy in Patients 40 Years and Younger With Femoroacetabular Impingement Syndrome: A Multicenter Comparative Analysis. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/23259671221144776

[227] Conservative therapy versus arthroscopic surgery of femoroacetabular impingement syndrome (FAI): a systematic review and meta-analysis. Journal of Orthopaedic Surgery and Research. 2022. DOI: 10.1186/s13018-022-03187-1

[228] The New Bern Chondrolabral Classification Is Reliable and Reproducible. Clinical Orthopaedics & Related Research. 2021. DOI: 10.1097/corr.0000000000001706

[231] Should the Capsule Be Repaired or Plicated After Hip Arthroscopy for Labral Tears Associated With Femoroacetabular Impingement or Instability? A Systematic Review. Arthroscopy. 2017. DOI: 10.1016/j.arthro.2017.06.030

[232] Interobserver and Intraobserver Reliability of the Radiographic Analysis of Femoroacetabular Impingement and Dysplasia Using Computer-Assisted Measurements. The American Journal of Sports Medicine. 2014. DOI: 10.1177/0363546514542797

[233] Minimally Invasive Hip Arthroscopy for Femoroacetabular Impingement Using Iliofemoral Ligament–Preserving Skip Capsulotomy for Cam Resection. Arthroscopy Techniques. 2025. DOI: 10.1016/j.eats.2025.103769

[234] Imaging in Hip Arthroscopy for Femoroacetabular Impingement. Clinics in Sports Medicine. 2016. DOI: 10.1016/j.csm.2016.02.002

[235] Preoperative Dynamic Hip Examination Under Fluoroscopic Guidance Enhances the Understanding of Femoroacetabular Impingement Pathology and Treatment Planning. Arthroscopy, Sports Medicine, and Rehabilitation. 2021. DOI: 10.1016/j.asmr.2021.07.015

[237] Severe Damage to the Ligamentous-Fossa-Foveolar Complex Is Common in Patients Undergoing Surgical Hip Dislocation for Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2026. DOI: 10.1097/corr.0000000000003825

[238] Association Between Severity of Chondrolabral Junction Breakdown and Functional Outcomes After Hip Arthroscopy for Acetabular Labral Tears. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241255950

[240] Magnetic Resonance Imaging and Magnetic Resonance Arthrography Are Both Reliable and Similar When Measuring Hip Capsule Thickness in Patients With Femoroacetabular Impingement Syndrome. Arthroscopy, Sports Medicine, and Rehabilitation. 2024. DOI: 10.1016/j.asmr.2023.100874

[241] Patients With a High Femoroepiphyseal Roof With Concomitant Borderline Hip Dysplasia and Femoroacetabular Impingement Syndrome Do Not Demonstrate Inferior Outcomes Following Arthroscopic Hip Surgery. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2022. DOI: 10.1016/j.arthro.2021.10.012

[242] Combined 3-Dimensional CT and Multidirectional CT Arthrography for Femoroacetabular Impingement and Hip Lesions: A Cross-sectional Study Comparing Imaging and Hip Arthroscopic Surgery Findings. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/23259671221143459

[245] Cams and Pincer Impingement Are Distinct, Not Mixed: The Acetabular Pathomorphology of Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2010. DOI: 10.1007/s11999-010-1347-z

[246] Systematic Review and Meta-analysis of Outcomes After Hip Arthroscopy in Femoroacetabular Impingement. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546517749475

[248] Are cam and pincer deformities as common as dysplasia in Japanese patients with hip pain?. The Bone & Joint Journal. 2014. DOI: 10.1302/0301-620x.96b2.32680

[250] Bilateral Femoroacetabular Impingement: What is the Fate of the Asymptomatic Hip?. Clinical Orthopaedics & Related Research. 2019. DOI: 10.1097/corr.0000000000000699

[251] Evaluation of Osseous Morphology of the Hip Using Zero Echo Time Magnetic Resonance Imaging. The American Journal of Sports Medicine. 2019. DOI: 10.1177/0363546519878170

[252] A Narrow Posterior Joint Space on a False Profile Radiograph Does Not Correlate With Posterior Joint Cartilage Degeneration in Hip Preservation Patients. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2020. DOI: 10.1016/j.arthro.2020.07.023

[254] Mirror Image Modeling of Acetabular Rim Thickness Differences in Patients With Unilateral Femoroacetabular Impingement Syndrome. Arthroscopy, Sports Medicine, and Rehabilitation. 2019. DOI: 10.1016/j.asmr.2019.06.001

[255] The Impact of Hip Arthroscopy on the Progression of Hip Osteoarthritis in Patients With Femoroacetabular Impingement Syndrome: A Systematic Review and Meta-analysis. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/23259671251326116

[258] Preoperative Duration of Symptoms Is Associated With Outcomes 5 Years After Hip Arthroscopy for Femoroacetabular Impingement Syndrome. Arthroscopy. 2019. DOI: 10.1016/j.arthro.2019.08.032

[259] Labral Disease Associated With Femoroacetabular Impingement: Do We Need To Correct The Structural Deformity?. The Journal of Arthroplasty. 2009. DOI: 10.1016/j.arth.2008.11.040

[260] Radiographic Findings of Femoroacetabular Impingement in National Football League Combine Athletes Undergoing Radiographs for Previous Hip or Groin Pain. Arthroscopy. 2012. DOI: 10.1016/j.arthro.2012.03.005

[261] Reliability in the Diagnosis of Femoroacetabular Impingement and Dysplasia Among Hip Surgeons. Arthroscopy. 2013. DOI: 10.1016/j.arthro.2013.09.034

[262] Paper 45: Preoperative MRI Offers Minimal Clinical Utility, Delays Access to Hip Arthroscopy, and Lacks Cost-Effectiveness in Patients Aged 40 or Under with Classic Femoroacetabular Impingement Syndrome: A Retrospective 5-Year Analysis. Orthopaedic Journal of Sports Medicine. 2022. DOI: 10.1177/2325967121s00609

[263] Timing From Symptom Onset to Hip Arthroscopy Does Not Affect Patient‐Reported Outcome Measures for the Treatment of Femoroacetabular Impingement in Adolescent Patients. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2023.03.028

[264] Quality of Life Trajectories in Patients with Femoroacetabular Impingement Syndrome After Arthroscopic Surgery: Impact of Osteoarthritis Severity. Journal of ISAKOS. 2025. DOI: 10.1016/j.jisako.2025.100478

[265] Poster 79: Contralateral Hip Disease Progression in Patients with Femoroacetabular Impingement: 10-year Follow-up Prospective Cohort. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/2325967125s00187

[266] Staged Bilateral Hip Arthroscopy for Femoroacetabular Impingement Syndrome: Index Surgery Patient Reported Outcome Measures Predict Contralateral Surgery Results at 2 Years. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2022.10.048

[267] Poster 225: Assessing Hip-RSI in Patients that Undergo Hip Arthroscopy for Femoroacetabular Impingement. Orthopaedic Journal of Sports Medicine. 2024. DOI: 10.1177/2325967124s00194

[269] Predictors of Length of Career After Hip Arthroscopy for Femoroacetabular Impingement in Professional Hockey Players. The American Journal of Sports Medicine. 2016. DOI: 10.1177/0363546516650649

[270] Five‐Year Outcomes of Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome Among Female Patients: Higher Body Mass Index Is Associated With Reduced Clinically Significant Outcomes. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2023.06.035