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Femoroacetabular impingement

109 citationsUpdated Sep 2026

Overview

Arthroscopic management of femoroacetabular impingement is an appropriate option for many cases, enabling correction with a low rate of associated morbidity and significant short-term functional improvement [5, 13, 14]. The procedure improves patient-evaluated outcomes [1] and demonstrates favorable and safe mid-term outcomes in patients aged less than 50 [76]. While only about half of patients achieve an excellent 12-month outcome [32], significant improvements in patient-reported outcomes are observed at a minimum of 2-year follow-up [24] and persist in women at 4-year follow-up [29]. Data substantiate successful outcomes with few complications, allowing most athletes to resume activities [23]. Although surgical outcomes are superior with shorter symptom duration, caution is warranted when interpreting these outcomes concerning athletic performance once back in the game [12].

The procedure yields favorable clinical outcomes and hip functional improvement in patients with bilateral femoroacetabular impingement syndrome, whether treated via staged bilateral hip arthroscopy at a minimum follow-up of 5 years [10] or simultaneous bilateral surgery in appropriately selected patients [64]. In patients with borderline dysplasia, observed outcomes are similar to those of a femoroacetabular impingement group with normal coverage [2]. Hip arthroscopy 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 [16]. Borderline hip dysplasia is not associated with significant differences in hip survivorship or patient-reported outcomes after primary hip arthroscopy, supporting its use as a durable and effective treatment in this population [33]. Patients with inflammatory joint disease also experience significant improvement in patient-reported outcomes at midterm follow-up [15].

Femoral version and combined version, as distinct measures, are not associated with outcomes after hip arthroscopy for femoroacetabular impingement syndrome [35]. Microfracture alone results in a greater or equivalent reoperation rate and inferior or equivalent patient-reported outcomes compared with other cartilage repair procedures for acetabular chondral lesions [74]. Femoroacetabular cam or pincher impingement deformity under-resection is the primary indication for revision arthroscopy, which results in decreased pain and improved function [77]. It is essential to use strict diagnostic and classification criteria to control clinical study design and generate high-quality outcome information [19]. The first national consensus-based best practice guidelines for the surgical and nonsurgical management of femoroacetabular impingement have been developed [9]. Future randomized controlled trials and large observational cohort studies will strengthen the evidence and improve informed decision making [46]. Indisputable clinical evidence to confidently support surgical intervention does not exist at this time, though progress is being made [83].

Anatomy & Pathophysiology

Definition and Mechanism

Femoroacetabular impingement (FAI) is defined as a dynamic mechanical conflict between the proximal femur and the acetabulum [50]. This condition represents a recently proposed mechanism causing abnormal contact stresses and potential joint damage around the hip [108]. Intra-articular FAI occurs when the femoral head-neck junction abuts against the acetabular rim [50]. The concept focuses more on motion than on axial loading of the hip [184]. FAI is a dynamic condition of the hip that can be a source of pain and disability and could potentially lead to arthritis [186]. In the majority of cases, a bony deformity or spatial malorientation of the femoral head or head/neck junction, acetabulum, or both cause FAI [108]. Supraphysiologic motion or high impact might cause FAI even with very mild bony alterations [108].

Types of Impingement

Three types of FAI are recognized: cam, pincer, and combined cam/pincer [18]. Combined cam/pincer deformities are common [18], and in most cases, cam and pincer impingement exist together [40].

Cam impingement is caused by abnormalities that are femoral based, such as an aspherical femoral head and reduced head-neck offset [18]. It results from an abnormally shaped, nonspherical femoral head with decreased head-neck offset abutting the acetabulum [40]. Specifically, cam impingement occurs when the anterosuperior femoral head-neck junction is prominent or the femoral neck has a diminished offset from the adjacent femoral head [58]. This type is most common in young males [38].

Pincer impingement is caused by acetabular-based disorders such as acetabular retroversion, global overcoverage, and acetabular protrusio [18]. It is abnormal contact between the acetabular rim and the femoral head-neck junction caused by acetabular overcoverage [40]. Pincer impingement occurs when the acetabular rim has an area of overcoverage causing impingement against the femoral neck with functional motion [58]. This type is most common in middle-aged females [38]. Acetabular overcoverage in pincer impingement may be global, as in coxa profunda, or more focal in the anterosuperior acetabulum, as in acetabular retroversion [40]. The area of overcoverage can be global, as with protrusio acetabuli, or localized to the anterior acetabulum as with acetabular retroversion [58]. Acetabular retroversion can be global or isolated [58]. In true global retroversion of the acetabulum, the posterior coverage of the acetabulum is deficient, with the entire acetabulum rotated or retroverted about the longitudinal axis [58]. In isolated retroversion of the acetabulum, the anterosuperior rim of the acetabulum extends farther around the femoral head whereas the remainder of the acetabulum has more normal morphology [58].

Pathomechanics and Injury Patterns

Impingement abnormalities can cause labral tears (labrochondral separation), degeneration, or ossification [18]. They can also cause acetabular cartilage delamination [18] and secondary osteoarthritis [18]. Hip morphology affects the pattern of acetabular cartilage wear, with more frequent and severe lesions in cam and mixed-type FAI [78].

In hip flexion, the aspherical head in cam impingement creates a shearing force along the acetabular cartilage, resulting in delamination [38]. With cam impingement, the impingement typically occurs in flexion and results in a shearing of the articular surface and avulsion of the labrum [40]. A typical injury pattern with cam impingement is a tear at the base of the labrum at the labral-chondral junction [58]. With cam impingement, the adjacent articular cartilage becomes injured because of compression from the femoral head with its relatively larger radius of curvature rotating into the acetabulum [58]. Frequently, the articular cartilage delaminates from the underlying subchondral bone, progressing from the acetabular rim in cam impingement [58]. In cam impingement, the acetabular labrum is relatively spared, with more injury incurred within the adjacent articular cartilage [58]. Avulsion of the labrum may also occur with cam impingement [38].

Pincer impingement results in intrasubstance tears of the labrum, typically in the anterosuperior quadrant [38]. Pincer impingement contact causes intrasubstance tears of the labrum [40]. The injury pattern with pincer impingement is created by the femoral neck abutting the acetabular rim and labrum during the extremes of motion [58]. In pincer impingement, the labrum is pinched between the bony surfaces and subsequently suffers more damage than the adjacent articular cartilage, which is relatively spared [58]. In pincer impingement, the anterosuperior femoral head is levered against the acetabular rim, and a contrecoup cartilage lesion may occur in the posteroinferior acetabulum [38]. As pincer impingement worsens, the femoral head can be levered from the socket causing chondral damage in the posteroinferior acetabulum (contrecoup injury) [40]. A "contrecoup" injury frequently is seen on the posterior femoral head and postero-inferior acetabulum owing to levering of the femoral neck on the acetabular rim with subsequent increased pressure on the posterior hip cartilage in pincer impingement [58]. Pincer impingement may worsen with time as the result of reactive bone growth at the acetabular rim or calcification of the labrum, effectively increasing the arc of overcoverage of the acetabulum [58].

The mechanical loading on the acetabular cartilage in cam-type hips is left unchanged regardless of labral size during walking and deep flexion [133]. 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 [120].

Etiology and Development

The aetiology of FAI could be genetic or acquired [186]. Probable causes of FAI include paediatric hip disease and injury to the proximal femoral physis due to heavy athletic activity during critical growth periods [186]. Structural deformity can occur secondary to the sequelae of pediatric hip disease such as slipped capital femoral epiphysis, Legg-Calvé-Perthes disease, and hip dysplasia [131]. Cam deformity can be secondary to pediatric hip diseases including SCFE and LCPD [50]. In most cases of primary FAIS, no history of disease is present, and the condition is likely caused by a combination of genetic and environmental factors [131]. A 2.8 relative risk of cam deformity in the siblings of affected individuals suggests additional genetic contributions [131].

Idiopathic cam deformity has been suggested to be the most common acquired hip deformity in adolescents [50]. The etiology of both SCFE and cam deformities may have association with the developing capital epiphysis during the rapid growth in adolescents [50]. Intense physical activity during adolescence may cause mechanical overloading across the epiphyseal plate, leading to an increase in the epiphyseal extension [50]. Increased cupping phenomenon would make the head-neck junction broader, flattening the physiological convexity, or even creating a convex cam morphology [50]. In SCFE, mechanical overloading would lead to epiphyseal displacement because of different baseline factors such as biochemical physeal abnormalities, obesity, posterior inclination of the epiphysis, among others [50].

Several studies suggest a link between participation in high-level sports at a young age and the development of symptomatic disease [131]. Studies of young athletes demonstrate a lack of cam deformity in skeletally immature individuals but a presence after physeal closure [131]. The repetitive stress that occurs in athletic activities is thought to influence physeal growth and potentially contribute to the development of deformity [131]. The etiology of cam deformity is unknown, although some authors have postulated that it may be a mild variant of slipped capital femoral epiphysis [58]. More commonly, cam deformity has been postulated to be a developmental abnormality of the lateral femoral physis, possibly related to activity level [58]. In a cross-sectional MRI study of adolescents, abnormal alpha angles were not found in any hips with open physes, but 14% of hips with closed physes had cam deformities [58]. The daily activity levels for patients with cam deformities were significantly higher than for those with no deformity [58].

Extra-articular Impingement

Intra-articular is the most common form of FAI and arises from anatomical variations of the femur or acetabulum [50]. Extra-articular FAI occurs because of relatively distant conflicts between the lesser trochanter and the ischium (ischiofemoral impingement), between the greater trochanter and the supra-acetabular region, or between the femoral neck and the anterior-inferior iliac spine (subspine impingement) [50].

Subspine impingement is an extra-articular form of impingement that occurs between the femoral head-neck junction and a prominent AIIS [101]. It has been reported to be more prevalent than previously thought, with a prevalence of 23.7% [101]. Three variants of AIIS morphology were described: type I, in which there was a smooth ilium wall between the most caudad level of the AIIS and the anterosuperior rim; type II, in which the AIIS prominence extended to the level or above the acetabular rim; and type III, in which the AIIS extended distally to the acetabular rim [101]. Pathologic AIIS morphology can be developmental (types I and II) or can arise following pelvic osteotomy or secondary to prior rectus femoris injury or avulsion (type III) [101].

Impingement between the lesser trochanter and the ischium (ischiofemoral impingement) and the great trochanter and the ilium (trochanteric-pelvic impingement) are other potential, although uncommon, sources of extra-articular impingement [101]. The etiology for ischiofemoral impingement is variable, which includes aging (muscle atrophy), female gender (increased width of pelvis), coxa profunda, coxa valga, valgus hip due to proximal femoral osteotomy, Legg-Calvé-Perthes disease, peritrochanteric fractures with involvement of ligamentum teres, abductor muscle injury causing uncompensated hip adduction during gait, and multiple or isolated exostoses [101]. Intra-articular steroid injection typically provides no relief or only partial relief of symptomatic extra-articular impingement [101]. Both open and arthroscopic resection have been shown to improve motion and alleviate pain for extra-articular impingement [101].

Epidemiology and Prevalence

The prevalence of FAIS deformity in asymptomatic adults is estimated at approximately 14%, with 24% in males and 5% in females [131]. Males are three to five times more likely to have cam deformities than are females, and the deformity also is more likely to be bilateral in males [131]. A review of 473 CT scans showed that 40% of asymptomatic hips had radiographic findings associated with FAI [84]. Radiographic findings associated with FAI are more common in men than in women [84]. A study of otherwise healthy asymptomatic adolescents demonstrated a 16.8% rate of cam deformity (defined as an α angle ≥55°), a 32.4% rate of pincer deformity (defined as a lateral center edge angle ≥40°), and a 6.1% rate of mixed-type deformity [84]. Cam morphology was substantially more common in males, and pincer deformities were equally distributed among males and females [84].

A high prevalence of radiographic findings is consistent with FAI, but poor correlation exists between radiographic FAI and degenerative radiographic changes [84]. In a study of 96 asymptomatic hips with radiographic findings consistent with FAI, 82.3% of the patients had remained free of radiographic arthritic changes at a mean follow-up of 18.5 years [84]. More than 90% of asymptomatic adolescents have at least one radiographic parameter suggesting FAI, and 50% have two [38]. The prevalence of coxa profunda has been demonstrated to be the same in asymptomatic patients as in those with diagnosed FAI [38]. Later studies have demonstrated a high rate of false-positive radiographic findings for FAI [38]. There is evidence to show that femoroacetabular impingement exists in asymptomatic patients [40]. A review by Frank et al. documented a 37% occurrence of radiographic femoroacetabular impingement in asymptomatic individuals [40]. The prevalence of radiographic FAI is even higher in the athletic population [40]. There is no indication for operative treatment in asymptomatic individuals with FAI [40]. Asymptomatic individuals with FAI should be followed if symptoms do arise [40].

In a study of patients under 50 years of age undergoing total hip replacement, 97% had radiographic signs of cam, pincer, or mixed type impingement after excluding those with developmental dysplasia of the hip, slipped capital femoral epiphysis, and Perthes disease [58]. A large, prospective, cross-sectional, population-based study found 6% of men and 2% of women to have cam deformities [58]. In the same population-based study, 42% of those who had hip replacements had evidence of a cam deformity [58]. In a comparison of radiographs of hips that had total hip arthroplasty (THA) for osteoarthritis to radiographs of nonarthritic hips, 20% of the arthritic hips had evidence of acetabular retroversion, although only 5% of the asymptomatic hips showed signs of retroversion [58]. In the Copenhagen Osteoarthritis Study, deep acetabular sockets had an adjusted risk ratio of 2.4 for the development of osteoarthritis [58].

A multicenter prospective study of patients undergoing surgical treatment for symptomatic FAI reported that 55% of the patients were female, 88% were Caucasian, the average age was 28.4 years, and the average BMI was 25.1 kg/m2 [84]. Cam-type FAI was most common (47.6%), followed by mixed type (44.5%) and pincer type (7.9%) in a multicenter prospective study of patients undergoing surgical treatment for symptomatic FAI [84].

Studies have reported an increased prevalence of femoroacetabular deformities in football, soccer, and hockey players compared with the general population [131]. Kapron et al. found 72% of collegiate football players to have an alpha angle of more than 50 degrees [58]. According to the data from the National Football League (NFL) Scouting Combine, 90% of players showed radiographic evidence of FAIS, of whom 31% were symptomatic and 69% were asymptomatic [131]. The greater the α angle, the more likely was the athlete to present with symptoms [131]. Hip impingement in those with FAIS may routinely occur at hip flexion angles below 90° in neutral rotation [129]. Males engage in hip impingement at higher flexion angles than females [129].

Progression to Osteoarthritis

FAI is now recognized as a common cause of hip dysfunction and secondary osteoarthritis [18]. The presence of symptomatic hip impingement in adolescence and young adulthood is believed to be one of the primary causes of osteoarthritis in patients younger than the age of 50 years [58]. There is an increasing body of evidence that cam impingement can predispose a hip to osteoarthritis [58]. In a longitudinal, prospective study, a cam deformity with an alpha angle of more than 60 degrees had an adjusted odds ratio of 3.67 for development of end-stage osteoarthritis [58]. In a longitudinal, prospective study, an alpha angle of more than 83 degrees had an adjusted odds ratio of 9.66 for development of end-stage osteoarthritis [58]. In a 20-year longitudinal study of 1003 women, each degree increase in the alpha angle over 65 degrees was associated with a 5% increase in the risk of developing osteoarthritis [58].

Classification

Morphologic Classification: Three types of femoroacetabular impingement are recognized: cam, pincer, and combined cam/pincer [18]. Cam impingement is characterized by femoral-based abnormalities such as an aspherical femoral head, reduced head-neck offset, or femoral retroversion [18]. Pincer impingement is characterized by acetabular-based disorders such as acetabular retroversion, global overcoverage, and acetabular protrusio [18]. Combined cam/pincer deformities are common in femoroacetabular impingement [18], whereas isolated pincer impingement is rare and often coexists with cam abnormalities [161].

Extraarticular Classification: Three general types of extraarticular femoroacetabular impingement based on locations of contact between the femur and pelvis are observed intraoperatively: Type I (anterior), Type II (posterior), and Type III (complex) [51].

Beck Classification: The Beck classification represents the current standard for arthroscopic evaluation of intraarticular disease in femoroacetabular impingement [95]. This system demonstrates substantial interobserver reliability for arthroscopic evaluation of intraarticular disease [95]. A proposed novel classification with only two disease categories may not adequately characterize the spectrum of intra-articular abnormalities in femoroacetabular impingement [95].

Other Considerations: Diagnostic criteria for femoroacetabular impingement syndrome are heterogeneous and imprecise [167]. The Oxford consensus on primary cam morphology and femoroacetabular impingement syndrome identified diagnostic criteria as one of seven prioritized research domains [20]. Statistical shape modeling can be used to examine and help define cam morphology in femoroacetabular impingement syndrome [135], where subtle morphologic differences may account for developing the syndrome [135]. Three-dimensional statistical shape modeling of hip morphology is more predictive of femoroacetabular impingement syndrome compared to traditional two-dimensional radiographic metrics [167]. Femoral neck rotation within the acetabulum combined with anteroposterior placement of the greater trochanter is the strongest predictor of symptomatic femoroacetabular impingement syndrome [167]. Hip morphology influences the pattern of articular cartilage damage in femoroacetabular impingement [153]. Understanding of hip disorder-specific chondral damage patterns may be useful for the development of arthroscopic classification of hip disorders [153].

Clinical Presentation

History and Symptoms

Patients with symptomatic femoroacetabular impingement typically present with an insidious onset of groin pain [6], which may follow minor trauma [18]. Most patients report activity-related groin pain exacerbated by hip flexion activities [18, 30]. Common functional limitations include difficulty with prolonged sitting, walking, running, or pivoting [18]. Pain is usually exacerbated by exercise and may be positional [40], with specific complaints regarding sitting, driving, or putting on socks and shoes [40]. Symptoms are further exacerbated by periods of hip flexion, such as prolonged sitting [107]. Mechanical symptoms secondary to labral and articular cartilage disease may also be reported [18]. Hip pain may occasionally radiate laterally toward the trochanteric region, medially into the adductor region, and rarely into the buttocks or down to the knee [107]. A significant delay in diagnosis is common, often accompanied by frequent inaccurate prior diagnoses [6]. Active adolescents and young adults reporting hip and/or groin pain should be assessed for femoroacetabular impingement syndrome [30].

Physical Examination

Restricted hip motion is a defining feature of symptomatic femoroacetabular impingement syndrome [30]. Affected individuals often have less than 100° of straight flexion and less than 10° of internal rotation with the hip at 90° of flexion [179]. Patients generally exhibit restricted hip internal rotation in 90° of flexion [18] and decreased internal rotation overall [40]. Internal rotation and abduction are limited in femoroacetabular impingement [25], while patients generally have more passive external rotation than internal rotation [38, 39]. Asymmetrical range of motion between the hips is noted on examination [40]. A mild, intermittent limp is common but can be extremely subtle, occurring in up to 75% of patients [179]. Abductor weakness on the affected side is often seen with a positive Trendelenburg sign [179]. Palpation of the hip typically does not reproduce tenderness [40].

Special tests and adjuncts aid in diagnosis, though no single pathognomonic finding exists for femoroacetabular impingement [17]. The anterior impingement test, defined as the reproduction of symptoms with passive flexion, adduction, and internal rotation [38, 39], is present in 88% of patients with symptomatic femoroacetabular impingement syndrome [179]. However, this test elicits pain but is not specific for femoroacetabular impingement [18] and may be positive in any patient with a labral or chondral injury [179]. The subspine impingement test is performed with the patient supine, where maximal anterior groin pain with direct hip flexion beyond 90° is consistent with subspine impingement [179]. The apprehension test may recreate pain in patients with symptomatic posterior impingement [179]. A FABER (flexion, abduction, external rotation) test may show increased knee-to-table distance on the affected side in patients with femoroacetabular impingement [40]. Intra-articular anesthetic injection is a useful diagnostic adjunct; substantial or complete relief signifies an intra-articular source of pathology [179]. Little to no pain relief following intra-articular injection warrants further investigation for extra-articular sources of impingement or other pelvic or lumbar pathology [179].

Demographics and Prevalence

The combined type of femoroacetabular impingement is the most common [38, 39]. Radiographic findings suggestive of femoroacetabular impingement have significant variations with respect to sex and age [67]. More than 90% of asymptomatic adolescents have at least one radiographic parameter suggesting femoroacetabular impingement, and 50% have two [38, 39]. The prevalence of cam and pincer deformity is 37% and 67% in asymptomatic patients, respectively [104]. In patients with hip pain, the prevalence of radiographic findings consistent with femoroacetabular impingement is 60.5% [104]. An incidence of 17% for femoroacetabular impingement was reported in 84 patients with groin pain seen by a general practitioner during a 1-year period [104]. Radiological evidence of symptomatic femoroacetabular impingement was not uncommon in Japanese patients with hip pain, with cam deformity findings being the most common [55]. Bilateral disease is seen in approximately 75% of patients but is symptomatic in fewer than 25% [179]. Approximately one in four patients with femoroacetabular impingement presents with symptoms in the contralateral hip [69]. Extra-articular impingement is a less common but increasingly recognized source of symptomatic impingement [30]. Patients with extra-articular femoroacetabular impingement have lower preoperative modified Harris hip scores compared to those with intra-articular femoroacetabular impingement [51].

Diagnostic Criteria and Imaging Context

The diagnosis of femoroacetabular impingement syndrome is made based on a combination of clinical symptoms, physical examination findings, and imaging studies [17]. A triad of clinical symptoms, examination findings, and radiographic findings consistent with femoroacetabular impingement is needed to reliably diagnose the condition [104]. Radiographic studies are mandatory for definite diagnosis and direction of treatment [25]. Imaging findings must be interpreted in the context of a high prevalence of cam and pincer morphology in the general population [54]. Patients presenting with hip pain and evidence of femoroacetabular impingement should be subjected to strict diagnostic scrutiny and evaluated in the sum of their clinical and radiological presentation [63]. Femoroacetabular impingement must be differentiated from dysplasia when evaluating a patient with hip pain, as the two conditions may coexist [30]. Clinical identification of combined impingement and dysplasia is imperative to potentially improve patient outcomes [114]. Extra-articular hip impingement syndromes should form part of the differential diagnoses alongside intra-articular pathology, particularly in younger patients with a non-arthritic hip [36].

Investigations

Clinical Diagnosis and History

The diagnosis of femoroacetabular impingement (FAI) syndrome relies on a combination of clinical symptoms, physical examination findings, and imaging studies [17]. No single pathognomonic finding exists for FAI, requiring clinical and physical examination findings to be viewed collectively [17]. Patients with symptomatic FAI typically present with insidious onset of groin pain, limited hip motion, and a significant delay in diagnosis with frequent inaccurate prior diagnoses [6]. Most patients with symptomatic impingement (80%) present with pain in the anterior groin or lateral hip [70]. Approximately 25% of patients with symptomatic impingement report pain in the lumbar spine, buttock, or referred pain to the knee [70]. Patients with symptomatic FAI frequently present with activity-related groin pain that is exacerbated by hip flexion activities [18].

Physical examination reveals restricted hip internal rotation in 90° of flexion [18]. The impingement test (flexion, adduction, internal rotation) elicits pain but is not specific for FAI [18]. Internal rotation and abduction are limited in femoroacetabular impingement, but radiographic studies are mandatory for definite diagnosis and direction of treatment [25]. Hip femoroacetabular impingement (FAI) is overwhelmingly the primary cause of revision surgery after hip arthroscopy, necessitating expert clinical evaluation and examination [11]. 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 [60].

Plain Radiography

Imaging studies play a key role in establishing the diagnosis of femoroacetabular impingement (FAI) [34]. Plain radiographs are key in the initial assessment of patients suspected of femoroacetabular impingement [113]. A systematic approach to preoperative imaging should include standing AP pelvis, false-profile, Dunn views, and frog-lateral views [72]. For an accurate standing AP pelvis view, the coccyx should be centered in the midline with the tip within 1 to 3 cm of the pubic symphysis and symmetric obturator foramen [72]. The AP pelvis view is used to assess acetabular anatomy, including version, acetabular coverage, and femoral head sphericity [18].

Specific radiographic signs include a "pistol-grip deformity," demonstrating a nonspherical femoral head, seen in cam impingement [38]. A crossover sign is classically seen with acetabular retroversion that causes pincer impingement [38]. In acetabular retroversion, the anterior wall crosses lateral to the posterior wall, creating a "crossover sign" [40]. The center-edge angle is the angle formed between a line perpendicular to the transverse axis of the pelvis passing through the center of the femoral head and a second line from the center of the femoral head to the lateral edge of the acetabular sourcil [40]. Center-edge angle values of less than 20 to 25 degrees may indicate acetabular undercoverage [40]. Lateral center edge angle (LCEA) values greater than 40° indicate pincer morphology [72].

The false-profile view provides additional radiographic information regarding acetabular morphology and is obtained with the patient rotated at an angle of 65° between the pelvis and x-ray source [72]. An anterior center edge angle greater than 40° on the false-profile view indicates excessive anterior overcoverage [72]. The Dunn and frog-lateral views are used for assessment of the femoral cam morphology [72]. The α angle is drawn to quantify the severity of asphericity, with values greater than 50° indicating cam deformity [72]. An alpha angle of more than 50 degrees is typical in hips with loss of sphericity [40]. The 45° Dunn view has been shown to be more sensitive in detecting the presence and severity of cam deformity than the 90° Dunn view [72]. When compared with the Dunn view, the frog-lateral view has improved specificity for cam morphology [72].

Radiographic findings on the AP pelvis concerning for acetabular undercoverage and structural instability include an LCEA less than 20° and a Tönnis angle greater than 10° [72]. On the false-profile view, an anterior center edge angle less than 20° is indicative of undercoverage [72]. Radiographic evidence of FAI is common in active patients with hip complaints [130]. The overall prevalence of radiographic findings consistent with FAI in young patients presenting with hip pain was 60.5% [160]. The prevalence of radiographic femoroacetabular impingement was common in Japanese patients who are generally considered to have dysplastic hips [150]. Radiographic findings suggestive of femoroacetabular impingement had significant variations with respect to sex and age in a study of 1878 asymptomatic hips [67].

CT

CT can give additional information about femur-acetabulum mismatch [38]. Computed tomography scans allow for accurate definition of deformities and are particularly helpful in revision hip arthroscopy [113]. Low-dose CT with three-dimensional reformats is particularly useful in surgical planning of complex or borderline deformities [18].

MRI

MRI or magnetic resonance arthrography provides information regarding the integrity of the acetabular labrum and articular cartilage [18]. MRI or magnetic resonance arthrography allows assessment of the anatomy of the proximal femur as well as the version of the acetabulum and femur [18]. The sensitivity of MRI to acetabular rim chondral lesions is limited [18]. Magnetic resonance arthrogram can be used to provide information about cartilaginous and labral injuries [38]. MRI is used to assess labral and chondral injuries [40]. In adolescent patients with symptomatic hip impingement, MRI may be useful to identify soft CAM lesions (non-ossified) that are under-represented on x-ray [146]. In adolescent patients with symptomatic hip impingement, MRI may be useful to identify soft CAM lesions (nonossified) that are under-represented on x-ray [154].

Other Considerations

All images routinely obtained in current clinical practice are 2-dimensional representations of complex 3-dimensional processes [54]. High-resolution, high magnet strength (minimum 3 Tesla), physiologic and/or biochemical dynamic MRI has the potential to image both soft and osseous tissues to best define hip impingement [54]. By incorporating advancements into routine imaging protocols, healthcare providers can ensure a comprehensive understanding of hip joint dynamics for patients with FAI and hip dysplasia [66].

The study demonstrated substantial prevalence of bony characteristics predisposing to femoroacetabular impingement in asymptomatic individuals according to established measurement parameters [41]. A study of asymptomatic adolescents demonstrated a 16.8% rate of cam deformity (defined as an α angle ≥55°) [84]. A study of asymptomatic adolescents demonstrated a 32.4% rate of pincer deformity (defined as a lateral center edge angle ≥40°) [84]. A study of asymptomatic adolescents demonstrated a 6.1% rate of mixed-type deformity [84]. Cam morphology was substantially more common in males than in females among asymptomatic adolescents [84]. Pincer deformities were equally distributed among males and females among asymptomatic adolescents [84]. Patients presenting with hip pain and evidence of FAI should be subjected to strict diagnostic scrutiny and evaluated in the sum of their clinical and radiological presentation [63]. There is no indication for operative treatment in asymptomatic individuals with radiographic FAI [40].

Treatment

Non-Operative

Nonoperative treatment remains the first line of management for most patients with femoroacetabular impingement and should not be abandoned in favor of early surgery [82]. Nonsurgical rehabilitation focuses on activity modification, treatment of physical impairments, and optimization of joint function [42]. Patients should minimize activities that place the hip in impingement positions, such as deep squatting, lunging, cycling, and hurdling [42]. Strengthening exercises must challenge the patient to control excessive adduction and internal rotation, emphasizing gluteal recruitment while minimizing tensor fascia lata use through resisted clam shells, sidesteps, unilateral bridges, and quadruped hip extension [42]. Treating hip flexor tightness is a priority because excessive tightness correlates with anterior pelvic tilt, which is associated with earlier occurrence of impingement in hip range of motion [42]. Joint mobilization is indicated when examination suggests loss of capsular mobility, while soft-tissue mobilization is useful when tissue restricts joint mobility with an elastic end-feel [42]. Hyaluronic acid is safe and effective for mild femoroacetabular impingement, providing significant pain reduction and function improvement [134]. Very low-quality evidence suggests hyaluronic acid and cell-based therapies may be beneficial [37]. Platelet-rich plasma is not associated with improved outcomes following hip femoroacetabular impingement surgery [37]. Patients with symptomatic labral tears can experience functional improvement after a minimum 1 year of nonsurgical treatment, regardless of the presence of femoroacetabular impingement [43].

Operative

Indications: Surgical intervention is recommended when patients have persistent hip pain interfering with sports participation for at least 3 months and symptoms are not resolved by nonsurgical treatments such as physical therapy, activity modification, intra-articular injections, and nonsteroidal antiinflammatory drugs [172]. Hip arthroscopy is an appropriate viable option only after failure to improve following a full course of physical therapy is established [82]. Before being recommended for surgery, patients with irreparable labral tears and femoroacetabular impingement syndrome undergo a minimum of 3 months of nonoperative treatment including rest, nonsteroidal antiinflammatory medications, and physical therapy [169]. The current literature does not support prophylactic cam or pincer decompression in asymptomatic patients [170]. No evidence exists on outcomes following non-operative management of femoroacetabular impingement with concomitant Tönnis Grade 2 or more osteoarthritis of the hip [173].

Surgical Approach / Technique: Both arthroscopic and open techniques are effective in the surgical management of femoroacetabular impingement syndrome [30]. Treatment of anterior femoroacetabular impingement through an arthroscopically assisted mini-open anterior approach can reduce pain and improve function in a short-term observation period [48]. Arthroscopic treatment with labral repair in female patients results in superior improvement in hip functional outcomes compared with labral debridement [126]. Comparable minimum 2-year patient-reported outcome scores are found between circumferential and segmental labral reconstruction for the management of irreparable labral tear and femoroacetabular impingement syndrome in the primary setting [169]. Patients undergoing hip arthroscopy and autologous matrix-induced chondrogenesis for femoroacetabular impingement syndrome and acetabular chondral lesions demonstrate improved patient-reported outcomes and low rates of secondary surgeries at short-term follow-up [45]. Failure to address all components of osseous impingement is a prime reason for continued pain and dysfunction following hip arthroscopy [30].

Other Considerations: Significant improvements in patient-reported outcomes are observed in women after hip arthroscopy at 4-year follow-up [29]. At a minimum 10-year follow-up, both female and male patients report significant improvements in all patient-reported outcomes and high satisfaction, with similar final functional scores [49]. Hip arthroscopy produces clinically meaningful outcomes in both competitive athletes and nonathletes [180]. Borderline hip dysplasia is not associated with significant differences in hip survivorship or patient-reported outcomes after primary hip arthroscopy, supporting its use as a durable and effective treatment in this population [33]. Outcomes for patients with borderline dysplasia are similar to those of a femoroacetabular impingement group with normal coverage [2]. Reduced pain and improved function are reported in 68% to 96% of patients following surgical treatment [170]. Approximately 75% of athletes return to competition at the same level or better after surgical treatment [170]. The presence of preoperative osteoarthritis (Tönnis grade ≥ 2 or Outerbridge grade ≥ 3) is the strongest predictor of poor outcome following hip arthroscopy [170]. Other factors associated with poorer outcomes include older age, longer duration of symptoms, more severe preoperative pain, and poorer functional scores [170]. Older age, preexisting osteoarthritis, and a longer duration of symptoms are risk factors for poor outcomes following surgical intervention [30]. In the absence of preexisting chondral disease, residual impingement is the leading cause of continued postoperative pain and revision surgery [170]. Residual deformity is a leading cause of continued pain after surgical management [30]. Hip femoroacetabular impingement is overwhelmingly the primary cause of revision surgery after hip arthroscopy [11]. Surgical outcomes are superior with shorter symptom duration [12]. Caution is warranted in interpreting surgical outcomes concerning athletic performance once back in the game [12]. There are both modifiable and non-modifiable pre-operative factors that predict a return to high functional status after hip arthroscopy at 2-year minimum follow-up [178]. Postoperative alpha angle is predictive of return to sport in athletes undergoing hip arthroscopy [172]. There is a severe lack of evidence on the athlete characteristics and clinical course of nonreturning athletes, and the rate of subsequent hip procedures is unknown [185]. The 7-year hip survival rate in hip dysplasia appears inferior compared with that reported in femoroacetabular impingement (78%) [47]. The incidence of hip arthroscopy has increased dramatically over the past 5 years, particularly for the indication of femoroacetabular impingement/osteoarthritis [142]. The long-term effect of hip arthroscopy and its potential to alter the natural history of femoroacetabular impingement syndrome and prevent early degenerative joint disease remain to be determined [170]. A recent 10-year outcome study on 145 patients reported a 76% survivorship following hip arthroscopy for femoroacetabular impingement [170]. Developing therapies that effectively and consistently restore durable articular cartilage to full-thickness cartilage defects of the acetabulum will be crucial to optimize long-term clinical success across all ages [124]. While most cases of extra-articular hip impingement are managed conservatively, surgical intervention is considered for refractory cases; although positive treatment outcomes are generally observed, variations in results exist and long-term follow-up studies are lacking [86]. Knowledge of extra-articular hip impingement syndromes is essential and should form part of the differential diagnoses alongside intra-articular pathology, particularly in the younger patient with a non-arthritic hip [36]. Subspinal impingement morphology was a frequent finding in patients with symptomatic femoroacetabular impingement through a three-dimensional dynamic study [24]. A decrease in femoral anteversion was considered a useful criterion to suspect subspinal impingement morphology [24]. The current management of femoroacetabular impingement by members of the Canadian Orthopaedic Association is limited by a lack of awareness of high-level evidence [26]. The prioritised statements outlined seven research domains for femoroacetabular impingement: (1) best practice physiotherapy, (2) rehabilitation progression and return to sport, (3) exercise intervention and load management, (4) primary cam morphology prognosis and aetiology, (5) femoroacetabular impingement syndrome prognosis and aetiology, (6) diagnostic criteria, and (7) screening [20]. Management of femoroacetabular impingement starts with good diagnosis, as the natural course is a precursor to hip osteoarthritis [4]. A recent randomized clinical trial reported that hip arthroscopy led to a greater clinically significant improvement than physical therapy [170]. The UK FASHIoN trial provided the first evidence to support a clinically significant difference in hip-related quality of life with surgical intervention over hip therapy [42]. A 2017 study demonstrated evidence to support the use of formal physical therapy interventions postoperatively versus self-directed rehabilitation for femoroacetabular impingement [42]. The letter argues that the cited prospective studies on nonoperative management of femoroacetabular impingement likely included patients with mild or borderline dysplasia incorrectly characterized as femoroacetabular impingement [159].

Complications

Other Considerations: The natural history of femoroacetabular impingement syndrome (FAIS) without treatment involves probable worsening of symptoms over time [192]. Preoperative duration of symptoms significantly influences surgical outcomes; 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 [80].

Contralateral Hip Involvement: 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]. Long-term follow-up data indicates a high prevalence of contralateral pathology. 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 [88]. Similarly, 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 [91]. 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 [90].

Radiographic Progression: Studies of patients undergoing hip arthroscopy for femoroacetabular impingement syndrome demonstrated increased radiographic progression of hip osteoarthritis over time [28].

Osteoarthritis Risk and Treatment Efficacy: It is currently unknown whether treatment for FAI syndrome prevents hip osteoarthritis [192]. There is no evidence that treatment for FAI syndrome alters the risk of subsequent osteoarthritis [192].

Simultaneous Bilateral Surgery: Simultaneous femoroacetabular impingement surgery does not lead to higher rates of complications, postoperative pain, analgesic use, or side effects [137].

Recovery

Functional milestones: Master athletes undergoing primary hip arthroscopy for femoroacetabular impingement syndrome achieve comparable patient-reported outcomes, achievement of clinically significant outcomes, and reoperation-free time-dependent survivorship to nonmaster athletes at long-term follow-up [73]. At a mean 12-year follow-up, hip arthroscopy for femoroacetabular impingement led to significant clinical improvement, with 55% PASS achievement [163].

Other Considerations: These findings support the use of hip arthroscopy as a durable and effective treatment for femoroacetabular impingement syndrome in patients with borderline hip dysplasia [33]. Propensity-matched patients with borderline hip dysplasia undergoing primary and revision hip arthroscopy for femoroacetabular impingement syndrome achieved similar minimum 5-year patient-reported outcomes, clinically significant outcomes, and reoperation-free survivorship [81]. The observed outcomes for patients with borderline dysplasia were similar to those of a femoroacetabular impingement group with normal coverage [2]. While favorable short-term and midterm clinical outcomes have been reported after arthroscopic treatment of prearthritic hip lesions, greater long-term follow-up is necessary to assess the efficacy of hip arthroscopic surgery in altering the natural history and progressive degenerative changes associated with femoroacetabular impingement [199].

Patients with a preoperative duration of femoroacetabular impingement syndrome-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 [80]. In an adolescent cohort of symptomatic femoroacetabular impingement patients who underwent hip arthroscopy, there is no difference in patient-reported outcome measures when analyzing symptom duration by arbitrary time intervals or as a continuous variable [198].

At a mean follow-up of 7.1 years, significant symptoms in the contralateral hip of patients with femoroacetabular impingement were present in approximately 50% of patients [88]. A prospective longitudinal cohort study demonstrated a 51% rate of significant symptomatic development in the contralateral femoroacetabular impingement hip at minimum 10-year follow-up, with 26% of patients experiencing symptoms at baseline [90]. At a mean follow-up of 6.7 years, significant symptoms in the contralateral hip of patients with femoroacetabular impingement are present in 50.7% of patients, while 49.3% remain asymptomatic or minimally symptomatic [91]. The incidence of a symptomatic labral tear in asymptomatic contralateral hips with femoroacetabular impingement was 9% during 2 years of follow-up [200].

Key Evidence

• [L4] Arthroscopic treatment of femoroacetabular impingement improves patient evaluated outcomes. [1] (10.1186/1471-2474-15-394)
• [L3] The observed outcomes were similar to those of a femoroacetabular impingement group with normal coverage. [2] (10.1177/03635465231161348)
• [L5] Management of Femoroacetabular Impingement starts with good diagnosis, as the natural course is a precursor to hip osteoarthritis. [4] (10.1177/2325967121s00848)
• [L4] Arthroscopic management of femoroacetabular impingement enables correction with a low rate of associated morbidity and significant short-term functional improvement. [5] (10.1016/j.otsr.2010.08.002)
• [L2] Patients with symptomatic femoroacetabular impingement typically present with insidious onset of groin pain, limited hip motion, and a significant delay in diagnosis with frequent inaccurate prior diagnoses. [6] (10.1007/s11999-008-0680-y)
• [L5] The study developed the first national consensus-based best practice guidelines for the surgical and nonsurgical management of femoroacetabular impingement. [9] (10.5435/jaaos-d-18-00041)
• [L3] Staged bilateral hip arthroscopy for bilateral femoroacetabular impingement syndrome yields favorable clinical outcomes with symptom relief and hip functional improvement at a minimum follow-up time of 5 years. [10] (10.1002/arj.70069)
• [L5] Hip femoroacetabular impingement (FAI) is overwhelmingly the primary cause of revision surgery after hip arthroscopy, and hip arthroscopic surgeons must become experts at clinical evaluation and examination. [11] (10.1016/j.arthro.2015.04.103)
• [L5] Surgical outcomes for femoroacetabular impingement syndrome are superior with shorter symptom duration, but caution is warranted in interpreting these outcomes concerning athletic performance once back in the game. [12] (10.1016/j.arthro.2022.01.029)
• [L4] Arthroscopic management of femoroacetabular impingement appears to be an appropriate option for many cases. [13] (10.1016/j.arthro.2010.04.040)
• [L4] Arthroscopic management of femoroacetabular impingement appears to be an appropriate option for many cases. [14] (10.1016/j.arthro.2010.04.041)
• [L2] Patients with inflammatory joint disease undergoing hip arthroscopy for femoroacetabular impingement syndrome experience significant improvement in patient-reported outcomes at midterm follow-up. [15] (10.1016/j.asmr.2025.101258)
• [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. [16] (10.1016/j.arthro.2024.08.022)
• [L4] [17] (10.5435/00124635-201300001-00005)
• [L5] It is essential to use strict diagnostic and classification criteria to control a clinical study design and to generate high-quality outcome information for arthroscopic femoroacetabular impingement management. [19] (10.2106/jbjs.15.01405)
• [Paper] The prioritised statements outlined seven research domains: (1) best practice physiotherapy, (2) rehabilitation progression and return to sport, (3) exercise intervention and load management, (4) primary cam morphology prognosis and aetiology, (5) femoroacetabular impingement syndrome prognosis and aetiology, (6) diagnostic criteria, and (7) screening. [20] (10.1136/bjsports-2022-106092)
• [L4] The data substantiate successful outcomes in the arthroscopic management of femoroacetabular impingement with few complications and most athletes were able to resume activities. [23] (10.1177/0363546511404144)
• [L4] All included studies found improvements in patient-reported outcomes after hip arthroscopy for femoroacetabular impingement syndrome at a minimum of 2-year follow-up. [24] (10.1016/j.arthro.2022.10.038)
• [L3] Internal rotation and abduction are limited in femoroacetabular impingement, but radiographic studies are mandatory for definite diagnosis and direction of treatment. [25] (10.1007/s00167-011-1553-6)
• [L4] The current management of femoroacetabular impingement by members of the Canadian Orthopaedic Association is limited by a lack of awareness of high-level evidence. [26] (10.1007/s00167-014-2882-z)
• [L4] Studies of patients undergoing hip arthroscopy for femoroacetabular impingement syndrome demonstrated increased radiographic progression of hip osteoarthritis over time. [28] (10.1177/23259671251326116)
• [L4] Significant improvements in patient-reported outcomes in women after hip arthroscopy for femoroacetabular impingement at 4-year follow-up were found. [29] (10.1007/s00167-021-06802-6)
• [L3] Only about half of patients undergoing hip arthroscopy for femoroacetabular impingement achieved an excellent 12-month outcome. [32] (10.1186/s13018-026-06887-0)
• [L4] These findings support the use of hip arthroscopy as a durable and effective treatment for femoroacetabular impingement syndrome in this population. [33] (10.1177/03635465251405728)
• [L5] Imaging studies play a key role in establishing the diagnosis of femoroacetabular impingement (FAI). [34] (10.5435/00124635-201300001-00006)
• [L3] Femoral version and combined version, as distinct measures, are not associated with outcomes after hip arthroscopy for femoroacetabular impingement syndrome. [35] (10.1177/03635465241303704)
• [L4] The knowledge of extra-articular hip impingement syndromes is essential and should form a part of the differential diagnoses alongside intra-articular pathology including femoro-acetabular impingement particularly in the younger patient with a non-arthritic hip. [36] (10.1007/s00264-017-3431-4)
• [L1] [37] (10.1016/j.asmr.2022.05.002)
• [L4] The study demonstrated substantial prevalence of bony characteristics predisposing to femoroacetabular impingement in asymptomatic individuals according to the established measurement parameters in current literature. [41] (10.1177/0363546509358320)
• [L4] Patients with symptomatic labral tears can experience functional improvement after a minimum 1 year of nonsurgical treatment in the presence and absence of femoroacetabular impingement. [43] (10.1177/0363546518814484)
• [L4] Patients who underwent hip arthroscopy and AMIC for the treatment of femoroacetabular impingement syndrome and acetabular chondral lesions demonstrated improved patient-reported outcomes and low rates of secondary surgeries at short-term follow-up. [45] (10.1016/j.arthro.2024.04.028)
• [L5] Future randomized controlled trials and large observational cohort studies targeted at clinical research deficiencies will strengthen the evidence and improve informed decision making regarding the management of symptomatic femoroacetabular impingement. [46] (10.5435/00124635-201300001-00010)
• [L3] Overall, the 7-year hip survival rate in hip dysplasia appears inferior compared with that reported in femoroacetabular impingement (78%). [47] (10.1177/0363546517713176)
• [Paper] Treatment of anterior femoroacetabular impingement through an arthroscopically assisted mini-open anterior approach can reduce pain and improve function in a short-term observation period. [48] (10.1007/s00402-008-0806-4)
• [L3] After undergoing hip arthroscopic surgery for femoroacetabular impingement syndrome, both female and male patients reported significant improvements in all PROs at a minimum 10-year follow-up and high patient satisfaction, with similar final functional scores. [49] (10.1177/03635465241302806)
• [L3] [51] (10.1007/s11999-014-4001-3)
• [L5] [54] (10.1016/j.arthro.2019.05.009)
• [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. [55] (10.1302/0301-620x.96b2.32680)
• [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. [60] (10.1016/j.arthro.2015.04.104)
• [L4] Patients presenting with hip pain and evidence of FAI should be subjected to strict diagnostic scrutiny and evaluated in the sum of their clinical and radiological presentation. [63] (10.1302/0301-620x.99b12.37081)
• [L3] Simultaneous bilateral hip arthroscopic surgery for the treatment of femoroacetabular impingement represents a safe treatment option, producing effective midterm outcomes in appropriately selected patients. [64] (10.1177/03635465241263597)
• [Paper] By incorporating these advancements into routine imaging protocols, healthcare providers can ensure a comprehensive understanding of hip joint dynamics, enabling more accurate diagnosis and effective management strategies for patients with FAI and HD, ultimately leading to improved clinical outcomes. [66] (10.2106/jbjs.rvw.24.00070)
• [L3] Radiographic findings suggestive of femoroacetabular impingement had significant variations with respect to sex and age in this study sample. [67] (10.1177/2325967120977892)
• [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)
• [L3] Master athletes undergoing primary hip arthroscopy for femoroacetabular impingement syndrome achieve comparable patient-reported outcomes, achievement of clinically significant outcomes, and reoperation-free time-dependent survivorship to nonmaster athletes at long-term follow-up. [73] (10.1177/03635465251395219)
• [L2] Based on the available data, microfracture alone results in a greater or equivalent reoperation rate and inferior or equivalent patient-reported outcomes compared with other cartilage repair procedures for acetabular chondral lesions in patients with femoroacetabular impingement syndrome. [74] (10.1016/j.arthro.2023.05.034)
• [L3] Hip arthroscopy for management of femoroacetabular impingement and labral tears in patients aged less than 50 demonstrates favorable and safe mid-term outcomes. [76] (10.5435/jaaos-d-17-00258)
• [L5] Femoroacetabular cam or pincher impingement deformity under-resection is the primary indication for revision arthroscopy, and revision surgery results in decreased pain and improved function. [77] (10.1016/j.arthro.2015.07.011)
• [L3] Hip morphology affects the pattern of acetabular cartilage wear, with more frequent and severe lesions in cam and mixed-type FAI. [78] (10.1097/corr.0000000000000649)
• [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. [80] (10.1016/j.arthro.2019.08.032)
• [L3] Propensity-matched patients with borderline hip dysplasia undergoing primary and revision hip arthroscopy for femoroacetabular impingement syndrome achieved similar minimum 5-year patient-reported outcomes, clinically significant outcomes, and reoperation-free survivorship. [81] (10.1016/j.arthro.2024.05.005)
• [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. [82] (10.1016/j.arthro.2023.05.009)
• [L5] The author states that indisputable clinical evidence to confidently support surgical intervention for femoroacetabular impingement does not exist at this time, though progress is being made with studies such as the one discussed. [83] (10.1016/j.arthro.2018.03.040)
• [L5] While most cases of extra-articular hip impingement are managed conservatively, surgical intervention is considered for refractory cases; although positive treatment outcomes are generally observed, variations in results exist and long-term follow-up studies are lacking. [86] (10.1530/eor-2023-0179)
• [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. [88] (10.1177/03635465221119509)
• [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. [90] (10.1177/2325967125s00187)
• [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. [91] (10.1177/2325967121s00278)
• [L5] The Beck classification represents the current standard for arthroscopic evaluation of intraarticular disease in femoroacetabular impingement, demonstrating substantial interobserver reliability, while the proposed novel classification with only two disease categories may not adequately characterize the spectrum of intra-articular abnormalities. [95] (10.1177/0363546513480110)
• [L3] [104] (10.1177/0363546520970914)
• [L5] [107] (10.5435/00124635-201300001-00004)
• [L5] [108] (10.1007/s11999-008-0646-0)
• [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. [113] (10.1016/j.csm.2016.02.002)
• [L5] Clinical identification of combined impingement and dysplasia is imperative to potentially improve patient outcomes. [114] (10.1002/arj.70215)
• [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. [120] (10.1177/0363546518787518)
• [L5] Developing therapies that effectively and consistently restore durable articular cartilage to full-thickness cartilage defects of the acetabulum will be crucial if we are to optimize long-term clinical success in the treatment of femoroacetabular impingement across all ages. [124] (10.1016/j.arthro.2018.08.001)
• [L1] Arthroscopic treatment of femoroacetabular impingement with labral repair in female patients resulted in superior improvement in hip functional outcomes compared with labral debridement. [126] (10.1016/j.arthro.2012.07.011)
• [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. [129] (10.1002/arj.70005)
• [L2] Radiographic evidence of FAI is common in active patients with hip complaints. [130] (10.1007/s11999-010-1233-8)
• [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. [133] (10.1177/2325967124s00154)
• [L4] Hyaluronic acid is safe and effective in the treatment of mild femoroacetabular impingement, with significant pain reduction and function improvement. [134] (10.1007/s00167-013-2581-1)
• [L4] The study provides a proof of concept that statistical shape modeling can be used to examine and help define cam morphology and that subtle morphologic differences may account for developing femoroacetabular impingement syndrome. [135] (10.1016/j.asmr.2019.11.005)
• [L3] Simultaneous femoroacetabular impingement surgery does not lead to higher rates of complications, postoperative pain, analgesic use, or side effects. [137] (10.1016/j.arthro.2013.09.079)
• [L3] The incidence of hip arthroscopy has increased dramatically over the past 5 years, particularly for the indication of FAI/OA. [142] (10.1016/j.arth.2013.02.039)
• [L3] In adolescent patients with symptomatic hip impingement, MRI may be useful to identify soft CAM lesions (non-ossified) that are under-represented on x-ray. [146] (10.1177/2325967121s00063)
• [L3] The prevalence of radiographic femoroacetabular impingement was common in Japanese patients who are generally considered to have dysplastic hips. [150] (10.1302/0301-620x.98b9.37267)
• [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. [153] (10.1007/s00167-014-3297-6)
• [L3] In adolescent patients with symptomatic hip impingement, MRI may be useful to identify soft CAM lesions (nonossified) that are under-represented on x-ray. [154] (10.1177/2325967121s00277)
• [L5] The letter argues that the cited prospective studies on nonoperative management of femoroacetabular impingement (FAI) likely included patients with mild or borderline dysplasia incorrectly characterized as FAI. [159] (10.1177/03635465221079311)
• [L3] The overall prevalence of radiographic findings consistent with FAI in young patients presenting with hip pain was 60.5%. [160] (10.1177/0363546519896355)
• [L5] The article details the modern understanding of the morphology, diagnosis, and arthroscopic treatment of pincer-type femoral acetabular impingement, addressing current controversies while noting that isolated pincer impingement is rare and often coexists with cam abnormalities. [161] (10.1016/j.csm.2016.02.003)
• [L3] At a mean 12-year follow-up, hip arthroscopy for femoroacetabular impingement led to significant clinical improvement, with 55% PASS achievement. [163] (10.1177/03635465241265721)
• [L3] Diagnostic criteria for FAIS are heterogeneous and imprecise; femoral neck rotation within the acetabulum combined with anteroposterior placement of the greater trochanter is the strongest predictor of symptomatic FAIS. [167] (10.1177/2325967123s00214)
• [L3] [169] (10.1016/j.arthro.2021.04.037)
• [L3] [172] (10.1016/j.arthro.2021.09.015)
• [L4] No evidence exists on outcomes following non-operative management of FAI with concomitant Tönnis Grade 2 or more OA of the hip. [173] (10.1007/s00167-022-07274-y)
• [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. [178] (10.1177/2325967118s00070)
• [L3] Hip arthroscopy for the treatment of FAIS in competitive athletes and nonathletes produced clinically meaningful outcomes in both patient groups. [180] (10.1177/0363546519885359)
• [L5] [184] (10.1097/01.blo.0000096804.78689.c2)
• [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. [185] (10.1177/0363546520956292)
• [L5] [186] (10.1302/2058-5241.3.170041)
• [Paper] [192] (10.1136/bjsports-2016-096743)
• [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. [198] (10.1016/j.arthro.2023.03.028)
• [L5] While favorable short-term and midterm clinical outcomes have been reported after arthroscopic treatment of prearthritic hip lesions, greater long-term follow-up is necessary to assess the efficacy of hip arthroscopic surgery in altering the natural history and progressive degenerative changes associated with FAI. [199] (10.1177/0363546513476281)
• [L4] The incidence of a symptomatic labral tear in these asymptomatic hips was 9% during 2 years of followup. [200] (10.1097/corr.0000000000000567)

See Also

• Hip arthroscopy
• Total hip replacement
• Hip osteoarthritis

References

[1] Outcome of arthroscopic treatment for symptomatic femoroacetabular impingement. BMC Musculoskeletal Disorders. 2014. DOI: 10.1186/1471-2474-15-394

[2] Long-term Outcomes After Arthroscopic Treatment of Femoroacetabular Impingement for Patients With Borderline Dysplasia. The American Journal of Sports Medicine. 2023. DOI: 10.1177/03635465231161348

[4] The Management of Femoroacetabular Impingement. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/2325967121s00848

[5] Assessment of arthroscopic management of femoroacetabular impingement. A prospective multicenter study. Orthopaedics & Traumatology: Surgery & Research. 2010. DOI: 10.1016/j.otsr.2010.08.002

[6] Clinical Presentation of Patients with Symptomatic Anterior Hip Impingement. Clinical Orthopaedics & Related Research. 2009. DOI: 10.1007/s11999-008-0680-y

[9] Best Practice Guidelines for Hip Arthroscopy in Femoroacetabular Impingement: Results of a Delphi Process. Journal of the American Academy of Orthopaedic Surgeons. 2020. DOI: 10.5435/jaaos-d-18-00041

[10] Midterm Outcomes of Staged Bilateral Hip Arthroscopy for Femoroacetabular Impingement Syndrome Show Comparable Outcomes Between Time Interval More or Less Than 12 Months of Bilateral Procedures. Arthroscopy. 2026. DOI: 10.1002/arj.70069

[11] Editorial Commentary: Hip Femoroacetabular Impingement Surgery Requires Improved Radiologic Research and Expert Understanding of Hip Clinical Examination. Arthroscopy. 2015. DOI: 10.1016/j.arthro.2015.04.103

[12] Editorial Commentary: Earlier Hip Arthroscopy May Result in Improved Outcomes for Femoroacetabular Impingement Syndrome in Symptomatic Athletes: No Time Like the Present Could Mean Better Luck Next Year. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2022.01.029

[13] Arthroscopic Management of Femoroacetabular Impingement with Two Year Follow‐up (SS‐30). Arthroscopy. 2010. DOI: 10.1016/j.arthro.2010.04.040

[14] Open Surgical Dislocation vs. Arthroscopic Approach to Femoroacetabular Impingement: A Prospective Comparison (SS‐31). Arthroscopy. 2010. DOI: 10.1016/j.arthro.2010.04.041

[15] Inferior Clinical Outcomes and Increased Conversion to Total Hip Arthroplasty Following Hip Arthroscopy for Femoroacetabular Impingement Syndrome in Patients With Inflammatory Joint Disease: A Minimum 5-Year Matched Cohort Study. Arthroscopy, Sports Medicine, and Rehabilitation. 2025. DOI: 10.1016/j.asmr.2025.101258

[16] Patients With Dysplasia Achieve Similar Outcomes and Survivorship to Nondysplastic Patients 10 Years After Hip Arthroscopy for Femoroacetabular Impingement. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.08.022

[17] Clinical Diagnosis of Femoroacetabular Impingement. Journal of the American Academy of Orthopaedic Surgeons. 2013. DOI: 10.5435/00124635-201300001-00005

[18] Aaos Comprehensive Orthopaedic Review 3. Nonarthroplasty Surgical Treatment of the Hip > I. Femoroacetabular Impingement.

[19] Classification and Diagnostic Criteria of Femoroacetabular Impingement Are Essential for Clinical Outcome Evaluation. Journal of Bone and Joint Surgery. 2016. DOI: 10.2106/jbjs.15.01405

[20] Oxford consensus on primary cam morphology and femoroacetabular impingement syndrome: part 2—research priorities on conditions affecting the young person’s hip. British Journal of Sports Medicine. 2022. DOI: 10.1136/bjsports-2022-106092

[23] Arthroscopic Management of Femoroacetabular Impingement in Athletes. The American Journal of Sports Medicine. 2011. DOI: 10.1177/0363546511404144

[24] Patient-Reported Outcomes Improve at 2-Year Minimum Follow-Up After Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Systematic Review. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2023. DOI: 10.1016/j.arthro.2022.10.038

[25] Can femoroacetabular impingement and hip dysplasia be distinguished by clinical presentation and patient history?. Knee Surgery, Sports Traumatology, Arthroscopy. 2011. DOI: 10.1007/s00167-011-1553-6

[26] Results of the PeRception of femOroaCetabular impingEment by Surgeons Survey (PROCESS). Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-2882-z

[28] 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

[29] Significant improvement after hip arthroscopy for femoroacetabular impingement in women. Knee Surgery, Sports Traumatology, Arthroscopy. 2021. DOI: 10.1007/s00167-021-06802-6

[30] Orthopaedic Knowledge Update Sports Medicine 6. Femoroacetabular Impingement > Summary.

[32] Excellent 12-month outcomes after hip arthroscopy for femoroacetabular impingement: role of spinopelvic alignment and hip morphology—a multicenter study. Journal of Orthopaedic Surgery and Research. 2026. DOI: 10.1186/s13018-026-06887-0

[33] Borderline Hip Dysplasia Not Associated With Significant Differences in Hip Survivorship or Patient-Reported Outcomes After Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Cohort Study With Minimum 10-Year Follow-up. The American Journal of Sports Medicine. 2026. DOI: 10.1177/03635465251405728

[34] Diagnostic Imaging of Femoroacetabular Impingement. Journal of the American Academy of Orthopaedic Surgeons. 2013. DOI: 10.5435/00124635-201300001-00006

[35] Exploring the Relationship Between Combined, Acetabular, and Femoral Version on Postoperative Outcomes 2 Years After Hip Arthroscopy for Femoroacetabular Impingement Syndrome. The American Journal of Sports Medicine. 2025. DOI: 10.1177/03635465241303704

[36] Current concepts in the diagnosis and management of extra-articular hip impingement syndromes. International Orthopaedics. 2017. DOI: 10.1007/s00264-017-3431-4

[37] Platelet‐Rich Plasma Is Not Associated With Improved Outcomes Following Hip Femoroacetabular Impingement Surgery: Very Low‐Quality Evidence Suggests Hyaluronic Acid and Cell‐Based Therapies May Be Beneficial—A Systematic Review of Biological Treatments. Arthroscopy, Sports Medicine, and Rehabilitation. 2022. DOI: 10.1016/j.asmr.2022.05.002

[38] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > FEMOROACETABULAR IMPINGEMENT > 2. Types (Fig. 4.33).

[39] Miller S Review Of Orthopaedics. FEMOROACETABULAR IMPINGEMENT > 2. Types (Fig. 4.33).

[40] Campbell S Operative Orthopaedics 4 Volume Set. ANTERIOR CRUCIATE AND ANTROLATERAL LIGAMENT RECONSTRUCTION (BOX 51.8) > FEMOROACETABULAR IMPINGEMENT.

[41] Computed Tomography Assessment of Hip Joints in Asymptomatic Individuals in Relation to Femoroacetabular Impingement. The American Journal of Sports Medicine. 2010. DOI: 10.1177/0363546509358320

[42] Orthopaedic Knowledge Update Sports Medicine 6. Hip Rehabilitation > Femoroacetabular Impingement Syndrome.

[43] Improvement in Functional Outcome Scores Despite Persistent Pain With 1 Year of Nonsurgical Management for Acetabular Labral Tears With or Without Femoroacetabular Impingement. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518814484

[45] Autologous Matrix‐Induced Chondrogenesis for the Treatment of Hip Acetabular Chondral Lesions Demonstrates Improved Patient Reported Outcomes and Low Rates of Secondary Surgeries at Short‐Term Follow‐Up: A Systematic Review. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.04.028

[46] Clinical Trials in Orthopaedics and the Future Direction of Clinical Investigations for Femoroacetabular Impingement. Journal of the American Academy of Orthopaedic Surgeons. 2013. DOI: 10.5435/00124635-201300001-00010

[47] A Traffic Light Grading System of Hip Dysplasia to Predict the Success of Arthroscopic Hip Surgery. The American Journal of Sports Medicine. 2017. DOI: 10.1177/0363546517713176

[48] Arthroscopically assisted anterior decompression for femoroacetabular impingement: technique and early clinical results. Archives of Orthopaedic and Trauma Surgery. 2009. DOI: 10.1007/s00402-008-0806-4

[49] Sex-Based Differences in the Arthroscopic Treatment of Femoroacetabular Impingement Syndrome: 10-Year Outcomes With a Nested Propensity-Matched Comparison. The American Journal of Sports Medicine. 2025. DOI: 10.1177/03635465241302806

[50] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Pediatric Hip Disorders > Femoroacetabular Impingement.

[51] 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

[54] 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

[55] 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

[58] Campbell S Operative Orthopaedics 4 Volume Set. HIP PAIN IN THE YOUNG ADULT AND HIP PRESERVATION SURGERY > FEMOROACETABULAR IMPINGEMENT.

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

[63] High prevalence of acetabular retroversion in asymptomatic adults. The Bone & Joint Journal. 2017. DOI: 10.1302/0301-620x.99b12.37081

[64] Midterm Outcomes After Simultaneous Hip Arthroscopic Surgery for Bilateral Femoroacetabular Impingement. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241263597

[66] Imaging Modalities in the Preoperative Assessment of Femoroacetabular Impingement and Hip Dysplasia: Determining Best Practices. JBJS Reviews. 2024. DOI: 10.2106/jbjs.rvw.24.00070

[67] Prevalence of Morphological Variations Associated With Femoroacetabular Impingement According to Age and Sex: A Study of 1878 Asymptomatic Hips in Nonprofessional Athletes. Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/2325967120977892

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

[70] Orthopaedic Knowledge Update Sports Medicine 6. Femoroacetabular Impingement > History.

[72] Orthopaedic Knowledge Update Sports Medicine 6. Femoroacetabular Impingement > Imaging > Plain Radiographs.

[73] Long-term Outcomes After Hip Arthroscopy for Femoroacetabular Impingement Syndrome in Master Athletes: A Propensity-Matched Study With Mean 10-Year Follow-up. The American Journal of Sports Medicine. 2026. DOI: 10.1177/03635465251395219

[74] Microfracture of Acetabular Chondral Lesions Is Not Superior to Other Cartilage Repair Techniques in Patients With Femoroacetabular Impingement Syndrome: A Systematic Review. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2023.05.034

[76] 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

[77] Editorial Commentary: Femoroacetabular Impingement Under‐resection Is the Primary Indication for Revision Arthroscopy. Arthroscopy. 2015. DOI: 10.1016/j.arthro.2015.07.011

[78] The Pattern of Acetabular Cartilage Wear Is Hip Morphology-dependent and Patient Demographic-dependent. Clinical Orthopaedics & Related Research. 2019. DOI: 10.1097/corr.0000000000000649

[80] 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

[81] Primary and Revision Hip Arthroscopy in Borderline Hip Dysplasia Shows Comparable Outcomes at a Minimum 5‐Year Follow‐Up. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.05.005

[82] 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

[83] Editorial Commentary: Femoroacetabular Impingement and Evidence: Are We There Yet?. Arthroscopy. 2018. DOI: 10.1016/j.arthro.2018.03.040

[84] Orthopaedic Knowledge Update. Slipped Capital Femoral Epiphysis and Femoroacetabular Impingement > Femoroacetabular Impingement > Epidemiology.

[86] Extra-articular hip impingement: subspine, iliopsoas, and ischiofemoral impingement. EFORT Open Reviews. 2025. DOI: 10.1530/eor-2023-0179

[88] 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

[90] 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

[91] 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

[95] Arthroscopic Classification of Acetabular Rim Labrochondral Disease: Letter to the Editor. The American Journal of Sports Medicine. 2013. DOI: 10.1177/0363546513480110

[101] Orthopaedic Knowledge Update Sports Medicine 6. Femoroacetabular Impingement > Types of Impingement > Extra-­articular Impingement.

[104] Incidence of Femoroacetabular Impingement and Surgical Management Trends Over Time. The American Journal of Sports Medicine. 2020. DOI: 10.1177/0363546520970914

[107] Femoroacetabular Impingement: Defining the Condition and its Role in the Pathophysiology of Osteoarthritis. Journal of the American Academy of Orthopaedic Surgeons. 2013. DOI: 10.5435/00124635-201300001-00004

[108] The Concept of Femoroacetabular Impingement: Current Status and Future Perspectives. Clinical Orthopaedics & Related Research. 2009. DOI: 10.1007/s11999-008-0646-0

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

[114] 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

[120] 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

[124] Editorial Commentary: Acetabular Cartilage Repair: A Critically Important Frontier in Hip Preservation. Arthroscopy. 2018. DOI: 10.1016/j.arthro.2018.08.001

[126] Arthroscopic Labral Repair Versus Selective Labral Debridement in Female Patients With Femoroacetabular Impingement: A Prospective Randomized Study. Arthroscopy. 2013. DOI: 10.1016/j.arthro.2012.07.011

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

[130] Radiographic Prevalence of Femoroacetabular Impingement in a Young Population with Hip Complaints Is High. Clinical Orthopaedics & Related Research. 2010. DOI: 10.1007/s11999-010-1233-8

[131] Orthopaedic Knowledge Update Sports Medicine 6. Femoroacetabular Impingement > Etiology.

[133] 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

[134] Femoroacetabular impingement: is hyaluronic acid effective?. Knee Surgery, Sports Traumatology, Arthroscopy. 2013. DOI: 10.1007/s00167-013-2581-1

[135] Evaluation of Statistical Shape Modeling in Quantifying Femoral Morphologic Differences Between Symptomatic and Nonsymptomatic Hips in Patients with Unilateral Femoroacetabular Impingement Syndrome. Arthroscopy, Sports Medicine, and Rehabilitation. 2020. DOI: 10.1016/j.asmr.2019.11.005

[137] Bilateral Hip Arthroscopy Under the Same Anesthetic for Patients With Symptomatic Bilateral Femoroacetabular Impingement: 1‐Year Outcomes. Arthroscopy. 2013. DOI: 10.1016/j.arthro.2013.09.079

[142] Trends in Hip Arthroscopy Utilization in the United States. The Journal of Arthroplasty. 2013. DOI: 10.1016/j.arth.2013.02.039

[146] SOFT TISSUE CAM IMPINGEMENT IN ADOLESCENTS: MRI REVEALS IMPINGEMENT LESIONS UNDERAPPRECIATED ON X-RAY. Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/2325967121s00063

[150] CT-based morphological assessment of the hip joint in Japanese patients. The Bone & Joint Journal. 2016. DOI: 10.1302/0301-620x.98b9.37267

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

[154] Soft Tissue CAM Impingement in Adolescents: MRI reveals impingement lesions underappreciated on x-ray (138). Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/2325967121s00277

[159] “Nonoperative Management of Femoroacetabular Impingement in Adolescents: Clinical Outcomes at a Mean of 5 Years: A Prospective Study”: Letter to the Editor. The American Journal of Sports Medicine. 2022. DOI: 10.1177/03635465221079311

[160] 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

[161] Pincer Impingement. Clinics in Sports Medicine. 2016. DOI: 10.1016/j.csm.2016.02.003

[163] Patient Factors Influencing Outcomes at 12-Year Follow-up of Hip Arthroscopy for Femoroacetabular Impingement. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241265721

[167] Poster 231: Three-Dimensional Statistical Shape Modeling of Hip Morphology is More Predictive of Femoroacetabular Impingement Syndrome Compared to Traditional Two-Dimensional Radiographic Metrics. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/2325967123s00214

[169] Comparable Minimum 2‐Year Patient‐Reported Outcome Scores Between Circumferential and Segmental Labral Reconstruction for the Management of Irreparable Labral Tear and Femoroacetabular Impingement Syndrome in the Primary Setting: A Propensity‐Matched Study. Arthroscopy. 2021. DOI: 10.1016/j.arthro.2021.04.037

[170] Orthopaedic Knowledge Update Sports Medicine 6. Femoroacetabular Impingement > Outcomes.

[172] Postoperative Alpha Angle Is Predictive of Return to Sport in Athletes Undergoing Hip Arthroscopy for Femoroacetabular Impingement. Arthroscopy. 2021. DOI: 10.1016/j.arthro.2021.09.015

[173] 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

[178] 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

[179] Orthopaedic Knowledge Update Sports Medicine 6. Femoroacetabular Impingement > Physical Examination.

[180] 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

[184] Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2003. DOI: 10.1097/01.blo.0000096804.78689.c2

[185] Can We Identify Why Athletes Fail to Return to Sport After Hip Arthroscopy for Femoroacetabular Impingement Syndrome? A Systematic Review and Meta-analysis. The American Journal of Sports Medicine. 2020. DOI: 10.1177/0363546520956292

[186] Hip arthroscopy for femoroacetabular impingement. EFORT Open Reviews. 2018. DOI: 10.1302/2058-5241.3.170041

[192] The Warwick Agreement on femoroacetabular impingement syndrome (FAI syndrome): an international consensus statement. British Journal of Sports Medicine. 2016. DOI: 10.1136/bjsports-2016-096743

[198] 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

[199] Hip Arthroscopic Surgery. The American Journal of Sports Medicine. 2013. DOI: 10.1177/0363546513476281

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