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Femoroacetabular impingement

119 citationsUpdated Oct 2026

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Overview¶

Arthroscopic management of femoroacetabular impingement (FAI) 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]. All included studies found improvements in patient-reported outcomes after hip arthroscopy for FAI syndrome at a minimum of 2-year follow-up [24]. Significant improvements in patient-reported outcomes in women after hip arthroscopy for FAI at 4-year follow-up were found [29]. The data substantiate successful outcomes in the arthroscopic management of FAI with few complications and most athletes were able to resume activities [23]. Surgical outcomes for FAI syndrome are superior with shorter symptom duration, but caution is warranted in interpreting these outcomes concerning athletic performance once back in the game [12]. Only about half of patients undergoing hip arthroscopy for FAI achieved an excellent 12-month outcome [31].

Hip arthroscopy for symptomatic FAI 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]. The observed outcomes were similar to those of a FAI group with normal coverage [2]. These findings support the use of hip arthroscopy as a durable and effective treatment for FAI syndrome in this population [32]. Patients with inflammatory joint disease undergoing hip arthroscopy for FAI syndrome experience significant improvement in patient-reported outcomes at midterm follow-up [15]. Arthroscopic management of FAI syndrome in patients aged ≥40 years results in significant and durable improvements in pain and function, with preservation of the native hip in most cases, although rates of conversion to total hip arthroplasty range from 2.9% to 13.2% across included studies [76]. Staged bilateral hip arthroscopy for bilateral FAI syndrome yields favorable clinical outcomes with symptom relief and hip functional improvement at a minimum follow-up time of 5 years [10]. Simultaneous bilateral hip arthroscopic surgery for the treatment of FAI represents a safe treatment option, producing effective midterm outcomes in appropriately selected patients [63].

Femoral version and combined version, as distinct measures, are not associated with outcomes after hip arthroscopy for FAI syndrome [33]. 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 FAI syndrome [73]. Femoral 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]. The study developed the first national consensus-based best practice guidelines for the surgical and nonsurgical management of FAI [9]. 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 FAI management [19]. 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 FAI [46]. The author states that indisputable clinical evidence to confidently support surgical intervention for FAI does not exist at this time, though progress is being made with studies such as the one discussed [83].

Anatomy & Pathophysiology¶

Definition and Mechanism¶

Femoroacetabular impingement (FAI) is defined as a dynamic mechanical conflict between the proximal femur and the acetabulum [49]. Intra-articular FAI occurs when the femoral head-neck junction abuts against the acetabular rim [49]. This condition is characterized by abnormal contact between the proximal femur and the acetabulum during terminal motion [40]. Such abnormal contact leads to damage of the acetabular labrum and articular cartilage [40]. FAI may lead to what was previously thought of as idiopathic osteoarthritis of the hip [40]. The concept of FAI focuses more on motion than on axial loading of the hip [186]. Supraphysiologic motion or high impact might cause FAI even with very mild bony alterations [109].

Types of Impingement¶

Three types of FAI are recognized: cam, pincer, and combined cam/pincer [18]. Combined cam/pincer deformities are common [18].

Cam Impingement Cam impingement is most common in young males [36]. It is caused by an aspherical femoral head and decreased head-neck offset [36]. The cam deformity is typically located anterolateral on the femoral neck [36]. 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 [57]. With flexion and particularly flexion combined with internal rotation, the nonspherical portion of the femoral head-neck junction rotates into the acetabulum [57]. In hip flexion, the aspherical head creates a shearing force along the acetabular cartilage resulting in delamination [36]. The adjacent articular cartilage becomes injured because of compression from the femoral head with its relatively larger radius of curvature rotating into the acetabulum [57]. The articular cartilage frequently delaminates from the underlying subchondral bone, progressing from the acetabular rim [57]. In cam impingement, the acetabular labrum is relatively spared, with more injury incurred within the adjacent articular cartilage [57]. A typical injury pattern is a tear at the base of the labrum at the labral-chondral junction [57]. Avulsion of the labrum may also occur [36].

Pincer Impingement Pincer impingement is most common in middle-aged females [36]. Pincer morphology is more commonly encountered in women [57]. It is caused by acetabular overcoverage that results in abnormal contact between the acetabular rim and femoral head-neck junction [36]. Pincer impingement occurs when the acetabular rim has an area of overcoverage causing impingement against the femoral neck with functional motion [57]. The area of overcoverage can be global, as with protrusio acetabuli, or localized to the anterior acetabulum as with acetabular retroversion [57]. Acetabular overcoverage may be due to protrusio acetabuli, coxa profunda, or acetabular retroversion [36]. In pincer impingement, the anterosuperior femoral head is levered against the acetabular rim [36]. The injury pattern is created by the femoral neck abutting the acetabular rim and labrum during the extremes of motion [57]. The labrum is pinched between the bony surfaces and subsequently suffers more damage than the adjacent articular cartilage, which is relatively spared [57]. Pincer impingement results in intrasubstance tears of the labrum, typically in the anterosuperior quadrant [36]. 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 [57]. A contrecoup cartilage lesion may occur in the posteroinferior acetabulum [36]. Pincer impingement may worsen with time as the result of reactive bone growth at the acetabular rim or calcification of the labrum [57].

Extra-Articular Impingement Extra-articular FAI occurs because of relatively distant conflicts between the lesser trochanter and the ischium, between the greater trochanter and the supra-acetabular region, or between the femoral neck and the anterior-inferior iliac spine [49]. Subspine impingement is an extra-articular form of impingement that occurs between the femoral head-neck junction and a prominent AIIS [101]. Subspine impingement 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 (smooth ilium wall), type II (AIIS prominence extended to the level or above the acetabular rim), and type III (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 sources of extra-articular impingement [101]. Ischiofemoral impingement can cause pain and restricted hip extension [101]. Trochanteric-pelvic impingement can cause pain and restricted hip abduction [101].

Etiology and Development¶

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 [134]. 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 [134]. The origin of cam deformities is controversial and has been the focus of investigations [49]. Cam deformity can be secondary to pediatric hip diseases including SCFE and LCPD [49]. Idiopathic cam deformity has been suggested to be the most common acquired hip deformity in adolescents [49]. The etiology of both SCFE and cam deformities may have an association with the developing capital epiphysis during the rapid growth in adolescents [49]. Intense physical activity during adolescence may cause mechanical overloading across the epiphyseal plate, leading to an increase in the epiphyseal extension [49]. Increased cupping phenomenon makes the head-neck junction broader, flattening the physiological convexity, or even creating a convex cam morphology [49]. In SCFE, mechanical overloading leads to epiphyseal displacement because of different baseline factors such as biochemical physeal abnormalities, obesity, and posterior inclination of the epiphysis [49]. A 2.8 relative risk of cam deformity in the siblings of affected individuals suggests additional genetic contributions [134]. Several studies suggest a link between participation in high-level sports at a young age and the development of symptomatic disease [134]. Studies of young athletes demonstrate a lack of cam deformity in skeletally immature individuals but a presence after physeal closure [134]. Repetitive stress that occurs in athletic activities is thought to influence physeal growth and potentially contribute to the development of deformity [134]. 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 [57]. The daily activity levels for patients with cam deformities were significantly higher than for those with no deformity [57].

Epidemiology and Prevalence¶

The prevalence of FAIS deformity in asymptomatic adults is estimated at approximately 14%, with 24% in males and 5% in females [134]. Males are three to five times more likely to have cam deformities than are females [134]. Cam deformity is also more likely to be bilateral in males [134]. 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°) [84]. The same study demonstrated a 32.4% rate of pincer deformity (defined as a lateral center edge angle ≥40°) in asymptomatic adolescents [84]. The same study demonstrated a 6.1% rate of mixed-type deformity in asymptomatic adolescents [84]. Cam morphology was substantially more common in males among asymptomatic adolescents [84]. Pincer deformities were equally distributed among males and females among asymptomatic adolescents [84]. More than 90% of asymptomatic adolescents have at least one radiographic parameter suggesting FAI [36]. 50% of asymptomatic adolescents have two radiographic parameters suggesting FAI [36]. A multicenter prospective study of patients undergoing surgical treatment for symptomatic FAI reported that 55% of the patients were female [84]. The average age of patients undergoing surgical treatment for symptomatic FAI was 28.4 years [84]. The average BMI of patients undergoing surgical treatment for symptomatic FAI was 25.1 kg/m2 [84]. Cam-type FAI was most common in surgical patients (47.6%), followed by mixed type (44.5%) and pincer type (7.9%) [84]. 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 [57]. A large, prospective, cross-sectional, population-based study found 6% of men and 2% of women to have cam deformities [57]. In the same population-based study, 42% of those who had hip replacements had evidence of a cam deformity [57]. 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 [57]. In the same longitudinal study, an alpha angle of more than 83 degrees had an adjusted odds ratio of 9.66 for development of end-stage osteoarthritis [57]. 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 [57]. In a comparison of radiographs of hips that had total hip arthroplasty for osteoarthritis to radiographs of nonarthritic hips, 20% of the arthritic hips had evidence of acetabular retroversion [57]. Only 5% of the asymptomatic hips showed signs of acetabular retroversion in the same comparison [57]. In the Copenhagen Osteoarthritis Study, deep acetabular sockets had an adjusted risk ratio of 2.4 for the development of osteoarthritis [57]. According to data from the National Football League (NFL) Scouting Combine, 90% of players showed radiographic evidence of FAIS [134]. Of NFL players with radiographic evidence of FAIS, 31% were symptomatic and 69% were asymptomatic [134]. The greater the α angle, the more likely was the athlete to present with symptoms in the NFL cohort [134]. Kapron et al. found 72% of collegiate football players to have an alpha angle of more than 50 degrees [57].

Clinical Presentation and Diagnosis¶

FAI is a clinical diagnosis supported by radiographic findings of proximal femoral or acetabular dysmorphology [84]. This condition typically manifests as anterior hip and/or groin pain with flexion-related activities [84]. Radiographic findings in the absence of symptoms are common [84]. Most patients with symptomatic impingement (80%) present with pain in the anterior groin or lateral hip [69]. Approximately 25% of patients report pain in the lumbar spine, buttock, or even referred pain to the knee [69]. Patients may display the classic "C" sign when describing the location of pain [69]. Most report an insidious onset of symptoms without a specific injury; however, athletes may recall a specific event [69]. Pain is often worse with activity (running, cutting, and pivoting) and is exacerbated in positions of hip flexion, such as prolonged sitting or squatting [69]. Patients with symptomatic FAI frequently present with activity-related groin pain that is exacerbated by hip flexion activities [18]. Patients may experience difficulty with prolonged sitting, walking, running, or pivoting [18]. The onset of symptoms is insidious or follows minor trauma [18]. Mechanical symptoms secondary to labral and articular cartilage disease may be present [18]. Patients with FAI will exhibit restricted hip internal rotation in 90° of flexion [18]. The impingement test (flexion, adduction, internal rotation) will elicit pain, but the test is not specific for FAI [18]. Groin or hip pain in association with limitation in ROM, especially flexion and internal rotation, can be a symptom [36]. Patients generally have more passive external rotation than internal rotation [36]. A positive result of an anterior impingement test is reproduction of symptoms with passive flexion, adduction, and internal rotation [36]. The diagnosis of femoroacetabular impingement (FAI) syndrome is made based on a combination of clinical symptoms, physical examination findings, and imaging studies [17]. No single pathognomonic finding exists for FAI [17]. Clinical and physical examination findings must be viewed collectively because no single pathognomonic finding exists for FAI [17]. 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 [56]. Physical examination in multiple positions and gait assessment are required to distinguish between intra-articular and extra-articular contributors to hip pain [56]. Given the overlap in symptomatology between the lumbar spine, hip, and pelvis, it is common for patients to present in a delayed fashion following previous failed treatment, or with an incorrect diagnosis [69]. A primary hip disorder may be obscured by compensatory injury to the pelvic musculature, lumbar spine, pubic joint, or sacroiliac joint as the patient attempts to maintain a high level of activity in the setting of restricted hip motion [69]. Patients may present with chronic gluteal pain, abductor irritability, trochanteric bursitis, osteitis pubis, or trochanteric bursitis [69]. Overlap between intra-articular and extra-articular pathology often occurs in patients presenting with lower abdominal groin or hip pain [70]. In 2012, using a cadaver model, it was shown that patients with FAI have increased stress placed on the pubic symphysis, which may predispose to combined FAI and athletic pubalgia [70]. Intra-articular steroid injection typically provides no relief or only partial relief of symptomatic extra-articular impingement [101].

Imaging and Radiographic Findings¶

Preoperative imaging is critical to the diagnosis of FAIS and in planning for potential surgical intervention [71]. A systematic approach should include standing AP pelvis, false-profile, Dunn views, and frog-lateral views [71]. For an accurate standing AP pelvis view, the pelvis should be aligned with neutral rotation and tilt such that the coccyx is centered in the midline [71]. The tip of the coccyx should be within 1 to 3 cm of the pubic symphysis on a well-centered AP pelvis view [71]. The obturator foramen should be symmetric on a well-centered AP pelvis view [71]. The joint space should be assessed for evidence of narrowing, sclerosis, or cystic change indicative of early osteoarthritis [71]. Acetabular depth and coverage should be assessed on the AP pelvis view [71]. Global overcoverage is easily identified when the medial femoral head lies adjacent to the ilioischial line (coxa profunda) or medial to it (coxa protrusio) [71]. Excessive anterior overcoverage, also referred to as cephalad retroversion, may be signaled by a crossover sign [71]. In cephalad retroversion, relative retroversion of the anterosuperior acetabulum coexists with normal version of the anteromedial acetabulum [71]. Cephalad retroversion must be differentiated from true acetabular

Classification¶

Intraarticular Morphology: 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/relative 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]. Statistical shape modeling can be used to examine and help define cam morphology [138], as subtle morphologic differences may account for developing femoroacetabular impingement syndrome [138].

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].

Extraarticular Contact: 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].

Other Considerations: Impingement abnormalities can cause labral tears, labrochondral separation, degeneration, or ossification [18], acetabular cartilage delamination [18], and secondary osteoarthritis [18]. Hip morphology influences the pattern of damage to the acetabular cartilage in femoroacetabular impingement [7], with hip damage occurring at the zone of femoroacetabular impingement [7]. Understanding of hip disorder-specific chondral damage patterns may be useful for the development of arthroscopic classification of hip disorders [159].

Strict diagnostic and classification criteria are essential to control clinical study design and generate high-quality outcome information for arthroscopic femoroacetabular impingement management [19]. The Oxford consensus on primary cam morphology and femoroacetabular impingement syndrome prioritized research domains including diagnostic criteria and screening [20]. Future clinical trials investigating the natural history and treatment of femoroacetabular impingement will require multimodal staging systems for hip osteoarthritis [45]. The optimal staging system for hip osteoarthritis in femoroacetabular impingement trials will differ based on study population size, specific objective, and expected time frame for end points [45].

Clinical Presentation¶

History and Symptoms¶

Patients with symptomatic femoroacetabular impingement typically present with an insidious onset of groin pain [6]. This onset may also follow minor trauma [18]. The pain is frequently activity-related and exacerbated by hip flexion activities [18]. Common complaints include pain with sitting, driving, or putting on socks and shoes [40]. Symptoms are generally exacerbated by periods of hip flexion, such as prolonged sitting [108]. Mechanical symptoms secondary to labral and articular cartilage disease are frequently 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 [108]. A significant delay in diagnosis with frequent inaccurate prior diagnoses is common in this population [6]. Active adolescents and young adults who report 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]. Patients exhibit restricted hip internal rotation in 90° of flexion [18]. Internal rotation and abduction are limited in femoroacetabular impingement [25]. Affected individuals often have less than 100° of straight flexion and less than 10° of internal rotation with the hip at 90° of flexion [181]. Palpation of the hip typically does not reproduce tenderness [40]. A mild, intermittent limp is common but can be extremely subtle, occurring in up to 75% of patients [181]. Abductor weakness on the affected side is often seen with a positive Trendelenburg sign [181].

Special tests and maneuvers provide further diagnostic insight. A positive anterior impingement test, performed with passive flexion, adduction, and internal rotation, reproduces symptoms in most patients (88%) with symptomatic femoroacetabular impingement syndrome [181]. However, the anterior impingement test is not specific for femoroacetabular impingement and may be positive in any patient with a labral or chondral injury [181]. The subspine impingement test, performed with maximal anterior groin pain with direct hip flexion beyond 90°, is consistent with subspine impingement [181]. 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 can be a useful adjunct to diagnosis, where substantial or complete relief signifies an intra-articular source of pathology [181]. Little to no pain relief following intra-articular injection warrants further investigation for extra-articular sources of impingement or other pelvic or lumbar pathology [181].

Demographics and Prevalence¶

Combined cam and pincer deformities are the most common type of femoroacetabular impingement [36, 37]. The prevalence of cam and pincer deformity is 37% and 67% in asymptomatic patients, respectively [104]. More than 90% of asymptomatic adolescents have at least one radiographic parameter suggesting femoroacetabular impingement, and 50% have two [36, 37]. Bilateral disease is seen in approximately 75% of patients, but is symptomatic in fewer than 25% [181]. Approximately one in four patients with femoroacetabular impingement presents with symptoms in the contralateral hip [67]. 16% of initially asymptomatic contralateral hips will develop symptoms during the next several years [67].

Diagnostic Criteria and Limitations¶

The diagnosis of femoroacetabular impingement syndrome is made based on a combination of clinical symptoms, physical examination findings, and imaging studies [17]. No single pathognomonic finding exists for femoroacetabular impingement, so clinical and physical examination findings must be viewed collectively [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 in femoroacetabular impingement [25]. Imaging findings must be interpreted in the context of a high prevalence of cam and pincer morphology in the general population [53]. 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 [62]. Femoroacetabular impingement must be differentiated from dysplasia when evaluating a patient with hip pain, as the two conditions may coexist [30]. Extra-articular hip impingement syndromes should form part of the differential diagnoses alongside intra-articular pathology, particularly in the younger patient with a non-arthritic hip [34].

Investigations¶

Clinical Diagnosis and History¶

Symptomatic femoroacetabular impingement (FAI) typically presents with insidious onset of groin pain, limited hip motion, and a significant delay in diagnosis, often accompanied by frequent inaccurate prior diagnoses [6]. Patients may report difficulty with prolonged sitting, walking, running, or pivoting [18]. Mechanical symptoms secondary to labral and articular cartilage disease are common in symptomatic FAI [18]. A layered approach should be applied to assess the mechanics of not only the hip joint but also the surrounding joints and musculature [69]. A primary hip disorder may be obscured by compensatory injury to the pelvic musculature, lumbar spine, pubic joint, or sacroiliac joint [69]. Because hip FAI is overwhelmingly the primary cause of revision surgery after hip arthroscopy [11], hip arthroscopic surgeons must become experts at clinical evaluation and examination [11]. Until radiologic criteria for FAI are confirmed, surgeons must rely on expert clinical examination, as sensitivity, specificity, and intraobserver and interobserver observational consistency for radiographic diagnosis require confirmation [59]. The current management of FAI by members of the Canadian Orthopaedic Association is limited by a lack of awareness of high-level evidence [26].

Plain Radiography¶

A systematic approach for preoperative imaging should include standing AP pelvis, false-profile, Dunn views, and frog-lateral views [71]. Plain radiographs are key in the initial assessment of patients suspected of FAI [115]. The AP pelvis view is used to assess acetabular anatomy, including version, acetabular coverage, and femoral head sphericity [18]. For an accurate standing AP pelvis view, the pelvis should be aligned with neutral rotation and tilt such that the coccyx is centered in the midline, the tip is within 1 to 3 cm of the pubic symphysis, and the obturator foramen is symmetric [71]. The anteroposterior pelvic view should be well centered, with the tip of the coccyx pointing to the symphysis pubis [40]. The distance between the coccyx and symphysis, on a well-centered view, should be 1 to 2 cm [40]. Coxa profunda is indicated when the acetabular teardrop lies medial to the ilioischial line [40]. If the femoral head lies medial to the ilioischial line, acetabular protrusion is indicated [40].

The LCEA can be used to assess lateral overcoverage on the AP pelvis view [71]. LCEA values greater than 40° indicate pincer morphology [71]. The center-edge angle is the angle formed between a line that is perpendicular to the transverse axis of the pelvis that passes 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]. Radiographic findings on the AP pelvis that are concerning for acetabular undercoverage and structural instability include an LCEA less than 20° and a Tönnis angle greater than 10° [71]. In some patients, including those with ligamentous hyperlaxity, more subtle signs of dysplasia (such as an LCEA less than 25°, uprising sourcil, anterior center edge angle less than 25°) may give rise to symptomatic instability [71]. It is crucial that all radiographs be scrutinized for evidence of acetabular dysplasia, which may coexist with FAIS or be the primary pathology in a patient presenting with hip pain [71].

Additional findings concerning for rim impingement include rim fractures, a downsloping sourcil, a Tönnis angle less than 0°, and impingement cysts or a trough along the femoral head-neck junction [71]. A crossover sign, combined with an ischial spine sign and a posterior wall sign (the posterior wall lies medial to the center of the femoral head), is indicative of true acetabular retroversion [71]. A crossover sign is classically seen with acetabular retroversion that causes pincer impingement [36]. In acetabular retroversion, the anterior wall crosses lateral to the posterior wall [36]. Cephalad retroversion must be differentiated from true acetabular retroversion, in which anterior overcoverage is associated with a deficient posterior wall [71]. True acetabular retroversion places the patient at risk for iatrogenic instability with isolated anterior wall decompression [71].

The false-profile view provides additional radiographic information regarding acetabular morphology [71]. The false-profile image is obtained with the patient rotated at an angle of 65° between the pelvis and x-ray source to profile the anterior acetabulum [71]. An anterior center edge angle greater than 40° on the false-profile view indicates excessive anterior overcoverage [71]. The morphology of the AIIS can be assessed with the false-profile view [71]. A false profile view is useful for evaluating anterior coverage, subspine deformities, and joint space narrowing [36]. Anterior coverage can be assessed using the false-profile view, on which an anterior center edge angle less than 20° is indicative of undercoverage [71].

The Dunn and frog-lateral views are used for assessment of the femoral cam morphology [71]. Various lateral views (most commonly 45° Dunn view and frog-leg lateral) can be used to assess femoral head sphericity and head-neck offset [18]. Most hip arthroscopy surgeons now prefer a 45-degree Dunn lateral view [36]. The α angle is drawn to quantify the severity of the asphericity on Dunn and frog-lateral views [71]. The alpha angle is determined on the lateral radiographs [40]. The alpha angle is formed by a line through the center of the femoral head and neck and a second line from the center of the femoral head to the point where the femoral head radius exits a concentric circle drawn around the femoral head [40]. α angle values greater than 50° indicate cam deformity [71]. 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 [71]. When compared with the Dunn view, the frog-lateral view has improved specificity for cam morphology [71]. A "pistol-grip deformity," demonstrating a nonspherical femoral head, is seen in cam impingement [36].

Later studies have demonstrated a high rate of false-positive radiographic findings [36]. Prevalence of coxa profunda has been demonstrated to be the same in asymptomatic patients as in those with diagnosed FAI [36]. More than 90% of asymptomatic adolescents have at least one radiographic parameter suggesting FAI, and 50% have two [36]. Radiographic evidence of FAI is common in active patients with hip complaints [133]. The overall prevalence of radiographic findings consistent with FAI in young patients presenting with hip pain was 60.5% [166]. Radiological evidence of symptomatic femoroacetabular impingement was not uncommon in Japanese patients with hip pain, with cam deformity findings being the most common [54]. The prevalence of radiographic femoroacetabular impingement was common in Japanese patients who are generally considered to have dysplastic hips [155]. Radiographic findings suggestive of femoroacetabular impingement had significant variations with respect to sex and age in a study sample of 1878 asymptomatic hips in nonprofessional athletes [120].

MRI¶

MRI or magnetic resonance arthrography provides information regarding the integrity of the acetabular labrum and articular cartilage [18]. The anatomy of the proximal femur as well as the version of the acetabulum and femur may be assessed with MRI or magnetic resonance arthrography [18]. Sensitivity to acetabular rim chondral lesions is limited with MRI or magnetic resonance arthrography [18]. Magnetic resonance arthrogram can be used to provide information about cartilaginous and labral injuries [36]. 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 [151]. In adolescent patients with symptomatic hip impingement, MRI may be useful to identify soft CAM lesions (nonossified) that are under-represented on x-ray [160]. High-resolution, high magnet strength (minimum 3 Tesla), physiologic and/or biochemical dynamic MRI has the potential to image both soft and osseous tissues, interacting to best define hip impingement [53].

Hip labral width less than 1 SD below the mean measured via preoperative MRI was associated with significantly worse functional outcomes after arthroscopic labral repair and treatment of femoroacetabular impingement [158]. Patients requiring revision surgery after primary hip arthroscopy for femoroacetabular impingement syndrome presented with smaller postoperative labral size (less than 1 mm difference) and greater reduction of labral size (at or less than 1mm difference) on MRI 12 months after primary surgery compared with those patients that did not require later revision surgery [153].

CT¶

Low-dose CT with three-dimensional reformats is particularly useful in surgical planning of complex or borderline deformities [18]. CT can give additional information about femur-acetabulum mismatch [36]. CT may help further define bony anatomy [40]. Computed tomography scans allow for accurate definition of deformities and are particularly helpful in revision hip arthroscopy [115]. Subspinal impingement morphology was a frequent finding in patients with symptomatic FAI through a three-dimensional dynamic study using computed tomography [24]. A decrease in femoral anteversion was considered a useful criterion to suspect subspinal impingement morphology [24]. Patients with femoroacetabular impingement syndrome who exhibited a higher femoral anteversion angle were at a greater likelihood of having a larger anterior labral length [27]. A study of hip CT scans in otherwise healthy asymptomatic adolescents demonstrated a 16.8% rate of cam deformity (defined as an α angle ≥55°) [84].

Other Considerations¶

The diagnosis of femoroacetabular impingement (FAI) syndrome requires that 3 prerequisites are met: patient symptoms, physical examination, and imaging [53]. Imaging, including plain radiographs, magnetic resonance imaging (MRI), and computed tomography, should be interpreted in the context of a high prevalence of cam and pincer morphology, in addition to labral injury, in the general population [53]. 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 femoroacetabular impingement is even higher in the athletic population [40]. There is no indication for operative treatment in asymptomatic individuals with radiographic femoroacetabular impingement [40]. Asymptomatic individuals with radiographic femoroacetabular impingement should be followed if symptoms do arise [40].

A high prevalence of radiographic findings is consistent with FAI, but poor correlation exists between radiographic FAI and degenerative radiographic changes [84]. One study evaluated 96 asymptomatic hips with radiographic findings consistent with FAI that had been treated with arthroplasty of the contralateral hip [84]. Because 82.3% of the patients in that study had remained free of radiographic arthritic changes at a mean follow-up of 18.5 years, the authors recommend against treatment of asymptomatic radiographic FAI [84]. 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]. These radiographic findings associated with FAI were more common in men than in women [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 [62]. 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 [34]. It is imperative to determine the source of the pain so that proper expectations and treatment options can be presented [70]. Clinical examination and detailed imaging can help to determine the combined diagnosis of FAI and athletic pubalgia [70]. All images routinely obtained in current clinical practice are 2-dimensional representations of complex 3-dimensional processes [53]. Although computerized modeling can dynamically manipulate femur and pelvis independently in fluoroscopy-, computed tomography-, and/or MRI-based collision detection models, the exact definition of “impingement” eludes the current literature [53]. By incorporating 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 [65].

Treatment¶

Non-Operative¶

Nonoperative treatment is the first line of management for most femoroacetabular impingement patients 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]. Reasonable training modifications are the initial recommendation, with activities that place the hip in a position of impingement minimized [42]. Combined positions of flexion, adduction, and internal rotation are commonly associated with increased symptoms [42]. Deep squatting, lunging, cycling, and hurdling are examples of activities that may require modification [42].

Strengthening exercises should be advanced to include weight-bearing activities that challenge the patient to control excessive adduction and internal rotation [42]. Exercises that maximize gluteal recruitment and minimize use of the tensor fascia lata are emphasized, as impaired strength of the abductors, external rotators, flexors, and extensors has been noted in these patients [42]. Strengthening lumbopelvic muscles is considered to decrease excessive anterior pelvic tilt associated with impingement secondary to altered acetabular orientation [42]. Flexibility activities treat muscle tightness that causes movement through symptomatic ranges of motion, with hip flexor tightness treated as a priority because excessive tightness is associated with anterior pelvic tilt and earlier occurrence of impingement in hip range of motion [42]. Clinicians must avoid placing the patient in positions associated with symptomatic impingement when prescribing stretching [42].

Joint mobilization is indicated when examination suggests a loss of capsular mobility, such as loss of passive range of motion, a capsular end-feel, or decreased symptoms with manual distraction [42]. Soft-tissue mobilization is useful when tissue restricts joint mobility, indicated by a loss of motion with an elastic end-feel and immediate response to manual treatment [42]. 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]. Hyaluronic acid is safe and effective for mild femoroacetabular impingement, providing significant pain reduction and function improvement [137]. Very low-quality evidence suggests hyaluronic acid and cell-based therapies may be beneficial [35]. Platelet-rich plasma is not associated with improved outcomes following hip femoroacetabular impingement surgery [35]. No evidence exists on outcomes following non-operative management of femoroacetabular impingement with concomitant Tönnis Grade 2 or more osteoarthritis [176]. Most cases of extra-articular hip impingement are managed conservatively, with positive treatment outcomes generally observed, although long-term follow-up studies are lacking [86].

Operative¶

Indications: Hip arthroscopy is an appropriate viable option only after failure to improve after a full course of physical therapy is established [82]. Surgical intervention is recommended if patients are diagnosed with labral pathology and femoroacetabular impingement and have persistent hip pain that interferes with sports participation for at least 3 months [175]. Symptoms are not resolved with nonsurgical treatments such as physical therapy, activity modification, intra-articular injections, and nonsteroidal antiinflammatory drugs in patients recommended for surgical intervention [175]. Before being recommended for surgery, all patients in a propensity-matched study underwent a minimum of 3 months of nonoperative treatment, which included rest, nonsteroidal antiinflammatory medications, and physical therapy [172]. Surgical intervention is considered for refractory cases of extra-articular hip impingement [86]. 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 recent randomized clinical trial reported that hip arthroscopy led to a greater improvement (clinically significant) than physical therapy [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]. Failure to address all the components of osseous impingement is a prime reason for continued pain and dysfunction following hip arthroscopy [30]. Residual deformity is a leading cause of continued pain after the surgical management of femoroacetabular impingement syndrome [30]. In the absence of preexisting chondral disease, residual impingement is the leading cause of continued postoperative pain and revision surgery [173]. Femoroacetabular cam or pincher impingement deformity under-resection is the primary indication for revision arthroscopy [77]. The article describes labral anatomy, clinical presentation, and provides guidelines for arthroscopic treatment of acetabular labral tears, emphasizing the need to address concurrent causes such as femoroacetabular impingement for good clinical outcomes [64].

Implant Selection: Arthroscopic treatment of femoroacetabular impingement with labral repair in female patients resulted in superior improvement in hip functional outcomes compared with labral debridement [129]. Comparable minimum 2-year patient-reported outcome scores were found between circumferential and segmental labral reconstruction for the management of irreparable labral tear and femoroacetabular impingement syndrome in the primary setting [172]. 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 [73]. Patients who underwent hip arthroscopy and autologous matrix-induced chondrogenesis 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 [74]. 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 [127].

Other Considerations: After undergoing hip arthroscopic surgery for femoroacetabular impingement syndrome, both female and male patients reported significant improvements in all patient-reported outcomes at a minimum 10-year follow-up and high patient satisfaction, with similar final functional scores [78]. Hip arthroscopy for management of femoroacetabular impingement and labral tears in patients aged less than 50 demonstrates favorable and safe mid-term outcomes [150]. Borderline hip dysplasia is not associated with significant differences in hip survivorship or patient-reported outcomes after primary hip arthroscopy for femoroacetabular impingement syndrome in a propensity-matched cohort study with minimum 10-year follow-up [32]. The observed outcomes of arthroscopic treatment for patients with borderline dysplasia were similar to those of a femoroacetabular impingement group with normal coverage [2]. Surgical outcomes for femoroacetabular impingement syndrome are superior with shorter symptom duration [12]. Caution is warranted in interpreting surgical outcomes concerning athletic performance once back in the game [12]. Hip arthroscopy for the treatment of femoroacetabular impingement syndrome in competitive athletes and nonathletes produced clinically meaningful outcomes in both patient groups [182]. 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 femoroacetabular impingement at 2-year minimum follow-up [180]. 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 [187]. The incidence of hip arthroscopy has increased dramatically over the past 5 years, particularly for the indication of femoroacetabular impingement/osteoarthritis [146]. Reduced pain and improved function are reported in 68% to 96% of patients following surgical treatment of femoroacetabular impingement syndrome [173]. Approximately 75% of athletes are able to return to competition at the same level or better following surgical treatment of femoroacetabular impingement syndrome [173]. 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 [173]. The current literature does not support prophylactic cam or pincer decompression in asymptomatic patients [173]. Recently, 10 years outcomes on 145 patients were reported with a 76% survivorship [173]. The presence of preoperative osteoarthritis (Tönnis grade ≥ 2 or Outerbridge grade ≥ 3) is the strongest predictor of poor outcome following hip arthroscopy [173]. Other factors associated with a poorer outcome following hip arthroscopy include older age, a longer duration of symptoms, more severe preoperative pain, and poorer functional scores [173]. Older age, preexisting osteoarthritis, and a longer duration of symptoms are risk factors for poor outcomes following surgical intervention for femoroacetabular impingement syndrome [30]. The 7-year hip survival rate in hip dysplasia appears inferior compared with that reported in femoroacetabular impingement (78%) [47]. Management of femoroacetabular impingement starts with good diagnosis, as the natural course is a precursor to hip osteoarthritis [4]. This article presents current concepts regarding the aetiology, clinical features, investigations, and management options for femoroacetabular impingement, discussing outcomes of both open and arthroscopic approaches [3]. Evidence for decision making and counseling in the contralateral hip for femoroacetabular impingement is lacking, particularly when the hip is asymptomatic [39]. 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]. This CORR Insights commentary discusses the natural history of femoroacetabular impingement, noting that untreated symptomatic impingement may lead to early arthritis and that while many adolescents respond to nonoperative management, an important subset requires surgical intervention [44]. 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 [165]. A 2017 study demonstrated evidence to support the use of formal physical therapy interventions postoperatively versus self-directed rehabilitation [42].

Revision: Revision surgery for femoroacetabular impingement results in decreased pain and improved function [77]. Hip femoroacetabular impingement is overwhelmingly the primary cause of revision surgery after hip arthroscopy [11].

Complications¶

Postoperative Outcomes and Revision¶

Symptom Duration: 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 [81].

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

Psychiatric Comorbidity: Psychiatric comorbidity was associated with increased failure rates and inferior clinical outcomes after hip arthroscopy for femoroacetabular impingement syndrome at a minimum 10-year follow-up [68]. There was a strong association between having a psychiatric condition and undergoing hip arthroscopy for femoroacetabular impingement, with an odds ratio of 3.4 (95% confidence interval 1.3-9.2, P < .01) compared to patients undergoing knee arthroscopy [183].

Specific Patient Populations¶

Dysplasia: Patients with dysplasia achieve similar outcomes and survivorship to nondysplastic patients 10 years after hip arthroscopy for femoroacetabular impingement, with 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 for femoroacetabular impingement syndrome at a minimum 10-year follow-up [32]. 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 [156].

Master Athletes: 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 [72].

Bilateral and Contralateral Disease¶

Contralateral Symptom Development: 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 [67]. 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]. 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].

Bilateral Surgery: Bilateral hip arthroscopy (either staged or simultaneous) for femoroacetabular impingement syndrome yields clinical outcomes and reoperation rates comparable with those of unilateral hip arthroscopy at a minimum 2-year follow-up [80]. Simultaneous femoroacetabular impingement surgery does not lead to higher rates of complications, postoperative pain, analgesic use, or side effects [140].

Natural History and Prognosis¶

Untreated Course: Without treatment, symptoms of FAI syndrome will probably worsen over time [194]. The natural course of femoroacetabular impingement is a precursor to hip osteoarthritis [4]. Untreated symptomatic impingement may lead to early arthritis [44].

Osteoarthritis Association: It is likely that cam morphology is associated with hip osteoarthritis [194]. Although the majority of participants with features of femoroacetabular impingement remained asymptomatic, those with features of femoroacetabular impingement had radiographic findings consistent with early osteoarthritis [21]. It is currently unknown whether treatment for FAI syndrome prevents hip osteoarthritis [194].

Recovery¶

Light activity (weeks): The provided evidence does not specify a typical week range for the resumption of desk work, driving, or light activities of daily living.

Full activity (months): The provided evidence does not specify a month range for the return to manual work, sport, or full range of motion and strength.

Complete recovery / outcome plateau (months): The provided evidence does not specify a month range for the stabilization of pain, strength, and final functional outcomes.

Rehabilitation protocol: The provided evidence does not detail physical therapy phasing, immobilisation duration, weight-bearing or range-of-motion progression, or sling/brace removal timing.

Functional milestones: Favorable outcomes were reported for the arthroscopic management of femoroacetabular impingement in the first 100 consecutive cases with a minimum 2-year follow-up [85]. Significant improvements in patient-reported outcomes in women after hip arthroscopy for femoroacetabular impingement were found at 4-year follow-up [29]. At a mean 12-year follow-up, hip arthroscopy for femoroacetabular impingement led to significant clinical improvement, with 55% PASS achievement [169].

Other Considerations: Long-term outcomes after arthroscopic treatment of femoroacetabular impingement for patients with borderline dysplasia were similar to those of a femoroacetabular impingement group with normal coverage [2]. Good outcome scores and a low conversion rate to total hip arthroplasty were observed 10 years after hip arthroscopy for the treatment of femoroacetabular impingement [92]. In a survivorship analysis comparing labral repair versus debridement 10 years after hip arthroscopy for femoroacetabular impingement, there was no difference in the likelihood of conversion to total hip arthroplasty or postoperative outcome scores between the two groups after adjusting for factors associated with conversion [92]. In patients with a preserved hip, there was improvement in patient-reported outcome scores at last follow-up 10 years after hip arthroscopy for femoroacetabular impingement [92].

While many adolescents respond to nonoperative management, an important subset requires surgical intervention for femoroacetabular impingement [44]. Patients with features of femoroacetabular impingement had radiographic findings consistent with early osteoarthritis, although the majority of participants remained asymptomatic [21]. 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 [202].

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]. 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]. 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]. The incidence of a symptomatic labral tear in asymptomatic contralateral hips with femoroacetabular impingement was 9% during 2 years of follow-up [203].

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 [81]. 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 [201].

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)
[L4] This article presents current concepts regarding the aetiology, clinical features, investigations, and management options for femoroacetabular impingement, discussing outcomes of both open and arthroscopic approaches. [3] (10.1007/s00264-011-1278-7)
[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)
[L2] Although the majority of these participants remained asymptomatic, those with features of femoroacetabular impingement had radiographic findings consistent with early osteoarthritis. [21] (10.1177/0363546517719460)
[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)
[L3] Patients with femoroacetabular impingement syndrome who exhibited a higher femoral anteversion angle were at a greater likelihood of having a larger anterior labral length. [27] (10.1177/23259671241265448)
[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. [31] (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. [32] (10.1177/03635465251405728)
[L3] Femoral version and combined version, as distinct measures, are not associated with outcomes after hip arthroscopy for femoroacetabular impingement syndrome. [33] (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. [34] (10.1007/s00264-017-3431-4)
[L1] [35] (10.1016/j.asmr.2022.05.002)
[L5] Evidence for decision making and counseling in the contralateral hip for femoroacetabular impingement (FAI) is lacking, particularly when the hip is asymptomatic. [39] (10.1177/0363546518810712)
[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)
[L5] This CORR Insights commentary discusses the natural history of femoroacetabular impingement (FAI), noting that untreated symptomatic impingement may lead to early arthritis and that while many adolescents respond to nonoperative management, an important subset requires surgical intervention. [44] (10.1097/corr.0000000000001646)
[L5] Future clinical trials investigating the natural history and treatment of femoroacetabular impingement will require multimodal staging systems for hip osteoarthritis because the optimal system will differ based on the size of the study population, the specific objective in question, and the time frame in which the investigator expects to see the specified end point. [45] (10.5435/00124635-201300001-00008)
[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)
[L5] Imaging studies play a key role in establishing the diagnosis of femoroacetabular impingement (FAI). [50] (10.5435/00124635-201300001-00006)
[L3] [51] (10.1007/s11999-014-4001-3)
[L5] [53] (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. [54] (10.1302/0301-620x.96b2.32680)
[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. [56] (10.1016/j.eats.2017.03.027)
[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. [59] (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. [62] (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. [63] (10.1177/03635465241263597)
[Paper] The article describes labral anatomy, clinical presentation, and provides guidelines for arthroscopic treatment of acetabular labral tears, emphasizing the need to address concurrent causes such as femoroacetabular impingement for good clinical outcomes. [64] (10.1016/j.csm.2010.12.006)
[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. [65] (10.2106/jbjs.rvw.24.00070)
[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. [67] (10.1177/2325967116s00176)
[L3] Psychiatric comorbidity was associated with increased failure rates and inferior clinical outcomes after hip arthroscopy for femoroacetabular impingement syndrome at a minimum 10-year follow-up. [68] (10.1177/03635465261480939)
[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. [72] (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. [73] (10.1016/j.arthro.2023.05.034)
[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. [74] (10.1016/j.arthro.2024.04.028)
[L4] Arthroscopic management of femoroacetabular impingement syndrome in patients aged ≥40 years results in significant and durable improvements in pain and function, with preservation of the native hip in most cases, although rates of conversion to total hip arthroplasty range from 2.9% to 13.2% across included studies. [76] (10.1002/arj.70557)
[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] 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. [78] (10.1177/03635465241302806)
[L3] Bilateral hip arthroscopy (either staged or simultaneous) for femoroacetabular impingement syndrome yields clinical outcomes and reoperation rates comparable with those of unilateral hip arthroscopy at a minimum 2-year follow-up. [80] (10.1002/arj.70641)
[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. [81] (10.1016/j.arthro.2019.08.032)
[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)
[L4] We report favorable outcomes for the arthroscopic management of femoroacetabular impingement in our early experience in the first 100 consecutive cases. [85] (10.1016/j.arthro.2011.05.018)
[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)
[L4] [92] (10.1097/corr.0000000000001778)
[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] [108] (10.5435/00124635-201300001-00004)
[L5] [109] (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. [115] (10.1016/j.csm.2016.02.002)
[L3] Radiographic findings suggestive of femoroacetabular impingement had significant variations with respect to sex and age in this study sample. [120] (10.1177/2325967120977892)
[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. [127] (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. [129] (10.1016/j.arthro.2012.07.011)
[L2] Radiographic evidence of FAI is common in active patients with hip complaints. [133] (10.1007/s11999-010-1233-8)
[L4] Hyaluronic acid is safe and effective in the treatment of mild femoroacetabular impingement, with significant pain reduction and function improvement. [137] (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. [138] (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. [140] (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. [146] (10.1016/j.arth.2013.02.039)
[L3] Hip arthroscopy for management of femoroacetabular impingement and labral tears in patients aged less than 50 demonstrates favorable and safe mid-term outcomes. [150] (10.5435/jaaos-d-17-00258)
[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. [151] (10.1177/2325967121s00063)
[L3] Patients requiring revision surgery after primary hip arthroscopy for femoroacetabular impingement syndrome presented with smaller postoperative labral size (less than 1 mm difference) and greater reduction of labral size (at or less than 1mm difference) on MRI 12 months after primary surgery compared with those patients that did not require later revision surgery. [153] (10.1016/j.arthro.2025.01.065)
[L3] The prevalence of radiographic femoroacetabular impingement was common in Japanese patients who are generally considered to have dysplastic hips. [155] (10.1302/0301-620x.98b9.37267)
[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. [156] (10.1016/j.arthro.2024.05.005)
[L4] Hip labral width less than 1 SD below the mean measured via preoperative MRI was associated with significantly worse functional outcomes after arthroscopic labral repair and treatment of femoroacetabular impingement. [158] (10.1016/j.arthro.2020.08.006)
[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. [159] (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. [160] (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. [165] (10.1177/03635465221079311)
[L3] The overall prevalence of radiographic findings consistent with FAI in young patients presenting with hip pain was 60.5%. [166] (10.1177/0363546519896355)
[L3] At a mean 12-year follow-up, hip arthroscopy for femoroacetabular impingement led to significant clinical improvement, with 55% PASS achievement. [169] (10.1177/03635465241265721)
[L3] [172] (10.1016/j.arthro.2021.04.037)
[L3] [175] (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. [176] (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. [180] (10.1177/2325967118s00070)
[L3] Hip arthroscopy for the treatment of FAIS in competitive athletes and nonathletes produced clinically meaningful outcomes in both patient groups. [182] (10.1177/0363546519885359)
[L3] [183] (10.1016/j.arth.2018.10.038)
[L5] [186] (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. [187] (10.1177/0363546520956292)
[Paper] [194] (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. [201] (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. [202] (10.1177/0363546513476281)
[L4] The incidence of a symptomatic labral tear in these asymptomatic hips was 9% during 2 years of followup. [203] (10.1097/corr.0000000000000567)

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

[3] Current concepts in the diagnosis and management of femoroacetabular impingement. International Orthopaedics. 2011. DOI: 10.1007/s00264-011-1278-7

[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

[7] Orthopaedic Knowledge Update Sports Medicine 6. Femoroacetabular Impingement > Annotated References.

[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

[21] Cam Deformities and Limited Hip Range of Motion Are Associated With Early Osteoarthritic Changes in Adolescent Athletes: A Prospective Matched Cohort Study. The American Journal of Sports Medicine. 2017. DOI: 10.1177/0363546517719460

[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

[27] Femoral Anteversion Angle as a Predictor of Anterior Hip Labral Length in Patients With Femoroacetabular Impingement Syndrome. Orthopaedic Journal of Sports Medicine. 2024. DOI: 10.1177/23259671241265448

[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.

[31] 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

[32] 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

[33] 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

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

[35] 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

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

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

[39] A Prospective Analysis of the Contralateral Hip Among Patients With Femoroacetabular Impingement: Response. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518810712

[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

[44] CORR Insights®: Does the Capital Femoral Physis Bony Morphology Differ in Children with Symptomatic Cam-type Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2021. DOI: 10.1097/corr.0000000000001646

[45] Staging of Hip Osteoarthritis for Clinical Trials on Femoroacetabular Impingement. Journal of the American Academy of Orthopaedic Surgeons. 2013. DOI: 10.5435/00124635-201300001-00008

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

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

[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

[53] 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

[54] 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

[56] Comprehensive Clinical Evaluation of Femoroacetabular Impingement: Part 1, Physical Examination. Arthroscopy Techniques. 2017. DOI: 10.1016/j.eats.2017.03.027

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

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

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

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

[64] Acetabular Labral Tears: Diagnosis, Repair, and a Method for Labral Reconstruction. Clinics in Sports Medicine. 2011. DOI: 10.1016/j.csm.2010.12.006

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

[68] Psychiatric Comorbidity Is Associated With Increased Failure Rates and Inferior Clinical Outcomes After Hip Arthroscopy for Femoroacetabular Impingement Syndrome at a Minimum 10-Year Follow-up. The American Journal of Sports Medicine. 2026. DOI: 10.1177/03635465261480939

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

[70] Orthopaedic Knowledge Update Sports Medicine 6. Core Muscle Injury/Athletic Pubalgia and Groin Pathology > Combined Athletic Pubalgia and Femoroacetabular Impingement.

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

[72] 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

[73] 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

[74] 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

[76] Hip Arthroscopy for Femoroacetabular Impingement Syndrome in Patients Aged ≥40 Years Produces Durable Functional Improvement With Moderate Survivorship Compared With Younger Cohorts: A Systematic Review. Arthroscopy. 2026. DOI: 10.1002/arj.70557

[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] 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

[80] Staged and Simultaneous Bilateral Hip Arthroscopy for Femoroacetabular Impingement Syndrome Achieves Clinical Outcomes Comparable With Unilateral Surgery at a Minimum 2‐Year Follow‐Up: A Systematic Review. Arthroscopy. 2026. DOI: 10.1002/arj.70641

[81] 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

[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.

[85] Arthroscopic Management of Femoroacetabular Impingement: Minimum 2‐Year Follow‐up. Arthroscopy. 2011. DOI: 10.1016/j.arthro.2011.05.018

[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

[92] Good Outcome Scores and Low Conversion Rate to THA 10 Years After Hip Arthroscopy for the Treatment of Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2021. DOI: 10.1097/corr.0000000000001778

[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

[108] 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

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

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

[120] 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

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

[129] 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

[133] 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

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

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

[138] 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

[140] 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

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

[150] 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

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

[153] Patients Requiring Revision Surgery After Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome Show a Small Reduction of Postoperative Labral Size: A Propensity‐Matched Controlled Study. Arthroscopy. 2025. DOI: 10.1016/j.arthro.2025.01.065

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

[156] 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

[158] Decreased Hip Labral Width Measured via Preoperative Magnetic Resonance Imaging Is Associated With Inferior Outcomes for Arthroscopic Labral Repair for Femoroacetabular Impingement. Arthroscopy. 2020. DOI: 10.1016/j.arthro.2020.08.006

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

[160] 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

[165] “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

[166] 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

[169] 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

[172] 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

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

[175] 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

[176] 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

[180] 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

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

[182] 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

[183] The Presence of a Psychiatric Condition is Associated With Undergoing Hip Arthroscopy for Femoroacetabular Impingement: A Matched Case-Controlled Study. The Journal of Arthroplasty. 2019. DOI: 10.1016/j.arth.2018.10.038

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

[187] 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

[194] 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

[201] 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

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

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

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