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Femoroacetabular impingement (FAI) syndrome is a symptomatic, motion related clinical disorder caused by premature contact between the acetabulum and the femoral head or head-neck junction1 causing repetitive microtrauma, labral disruption and degeneration of the femoroacetabular joint.

A triad of (1) symptoms, (2) clinical signs and (3) imaging findings might all be present to diagnose the FAI syndrome.1,2


Potential etiologies for Pincer-related FAI are protrusio acetabuli, coxa profunda, acetabular retroversion and prominent posterior acetabular rim. Slipped capital femoral epiphysis, Legg-Calve-Perthes disease, developmental hip dysplasia, prior femoral neck fracture with malunion, prior periacetabular or femoral osteotomy, femoral retrotorsion and coxa vara are possible etiologies for Cam-related FAI.3,4,5,6

Epidemiology, risk factors and primary prevention

Radiographic abnormalities associated with FAI have been noted in up to 35% of the general population.6,7 Radiographic evidence of FAI was present in 36% of patients under the age 55 with hip replacement due to OA.8 Cam-type impingement is more typical in young active males, while Pincer-type impingement is predominant in middle-aged athletic females.5,7,9 Isolated cam or pincer lesions present approximately 14% of the time, while approximately 86% are mixed lesions.3,7

Risk factors for FAI syndrome include the aforementioned etiologies but recent, studies suggest that high impact sports may play a role in development of Cam deformities during skeletal maturation.2


The hip is susceptible to impingement at terminal range of motion10 but abnormal morphologies promote this premature contact. The most commonly described abnormal morphologies are: (1) abnormally shaped femoral head or head-neck junction, termed Cam morphology and (2) excessive acetabular coverage of the femoral head, termed Pincer morphology.3,7

FAI syndrome caused by Cam-type morphology leads to increased pressure at the acetabular margins with hip flexion and internal rotation.4,6,11 FAI syndrome caused by Pincer-type morphology can result in acetabular cartilage and labrum damage.9,12,13

Clinical features and presentation over time

The majority of patients report an insidious, moderate to severe, aching or sharp pain. The most common location is the groin, followed by the lateral hip, thigh, buttock and lower back. Occasionally a specific trauma can be identified. Mechanical symptoms such as pop, snap, catch or locking and functional limitations such as limping during ambulation, limitation in walking distance, stair climbing and sitting tolerance have been described. The symptoms are exacerbated with activity and prolonged sitting and improve with rest and position changes.

Adequately treated patients usually improve and regain their usual activity level but untreated patients experience gradual deterioration. The long-term outlook for patients with FAI syndrome is still unknown.1

Associated conditions and complications

FAI is often found in association with labral tears, chondral injuries, and osteoarthritis.14

Prospective cohort studies demonstrated association between Cam morphologies and hip OA but the same association has not been found in Pincer morphologies.15



A detailed history is necessary to suspect FAI syndrome. History of congenital malformations, pediatric hip pathology, femoral fractures, musculoskeletal disorders and systemic diseases should be explored. Participation in sports and recreational activities, including goals and expectations are important to develop a treatment plan that improves functionality.16

Physical examination

A comprehensive hip and groin examination is essential to diagnose FAI syndrome. Evaluation of the 5 components of the hip joint: (1) osseous, (2) capsulolabral, (3) musculotendinous, (4) neurovascular and (5) kinematic chain are important to develop an adequate differential diagnosis.1,16

A decrease in range of motion and muscle strength in hip adduction, flexion and internal rotation are the most described physical impairments

The most common special tests to assess for FAI include the anterior impingement test known as FADDIR and the posterior impingement test.16 The dynamic internal rotation (DIRI) and external rotation (DEXRIT) impingement tests, Drehmann’s sign and FABER distance test are also described in the literature.3,16

Functional assessment

FAI syndrome limits activities involving hip flexion and internal rotation. Patients may report pain that affects their gait and mobility, especially squatting, rising from a seated position and walking up and down stairs.17 Abnormal movement pattern has also been described reflecting poor neuromuscular control during single leg standing or small knee bend motor control test. FAI should not interfere with self-care.


Plain radiograph of the pelvis in anteroposterior view allows assessment of the acetabular morphology. Cross table, lateral or frog leg are needed to assess the femoral neck.3,18 A faux profile view is used to quantify acetabular overcoverage and to assess the posteroinferior hip joint.

Magnetic resonance imaging (MRI) and magnetic resonance arthrography (MRA) are useful to evaluate labral/chondral pathology. Computed tomography and MRI are better for characterizing abnormal joint morphologies.1

The sonographic examination as diagnostic technique for FAI syndrome still is of limited use.

Early predictions of outcomes

The available literature is insufficient to determine if FAI syndrome has a greater risk of developing hip OA than isolated Cam morphologies or to predict who will develop hip osteoarthritis (OA), chondral or labral damage.


FAI is often related to participation in high impact sports during bone maturation or with activities that require a wide hip range of motion.15 Activities where FAI is commonly encountered involve kicking, cutting and sprinting, such as soccer, football, basketball and tennis.17 It has been theorized that altering activity levels during adolescence could prevent Cam morphologies, thereby eliminating this risk factor for OA, however there are no studies to support this theory.15

Social role and social support system

Taking this into account that sports participation may be affected in patients with FAI syndrome a support system could be composed of the family members, therapist, coach or athletic trainer and orthopedic surgeon if surgical procedure is being considered.


Available or current treatment guidelines

There is no definite treatment established for FAI syndrome. Treatment strategies include conservative care, physiotherapy-led rehabilitation and surgery.1 Available literature has been unable to compare effectiveness of these strategies or to determine their effects. A multidisciplinary team is recommended to support the patient during informed decision making process.1,19

Conservative care for FAI syndrome includes education, activity modifications to avoid hip impingement, oral analgesia, intra-articular steroid injection and watchful waiting. The published literature considers a conservative care trial as appropriate.20 Intra-articular steroid injection can be considered as conservative care, but this intervention is also a diagnostic instrument to confirm intra-articular hip pathology.1

Physiotherapy-led rehabilitation pretends to reduce symptoms and physical impairments, improving range of motion, strength and restoring neuromuscular control.20 A staged approach of exercise-based programs focusing on the core hip musculature is used in the literature.11,20 Almost half of available articles reviewing non-operative treatment of FAI promote the physiotherapy-led rehabilitation.20

Surgical management consists of open surgical dislocation with osteoplasty or arthroscopic techniques to correct the hip morphology and to repair the labral injury or chondral lesion if present.14, The available data is insufficient to determine benefits and safety due to the lack of randomized control trials.

Post-operative rehabilitation must take into account weight bearing and range of motion restriction and a step-wise progression to activity. Due to a small number of studies, great variability in the protocols and poorly reported outcomes, the optimal post-operative rehabilitation protocol has not been determined.

At different disease stages

Early: The first line treatment for femoral acetabular syndrome is medical/rehabiliative.11 This includes activity modification, restriction of athletic activity, avoidance of hip motions that exacerbate symptoms, and NSAID medications. Physical therapy should be utilized, but certain passive range of motion and stretching can actually worsen symptoms, so therapy should focus more on strengthening and patient education.6,10 The goal of treatment is to decrease the mechanical contact between the acetabulum and femoral neck.11

Middle: Intra-articular steroid injection is controversial but might confirm intra-articular pathology and relieve symptoms.5 Since femoral acetabular impingement occurs in an active population, activity modification and refraining from athletics can be difficult. Persistent symptoms require further physical therapy attempts.

Late: If medical treatments fail then surgical intervention can be considered. Surgical intervention typically consists of either open surgical dislocation with osteoplasty or arthroscopic techniques. Post-operatively, rehabilitation must take into account weight-bearing restrictions, range of motion restriction and a step-wise progression to activity. At a minimum, pain, loss of motion, muscle strength and proprioception around the hip should be addressed.20

Coordination of care

In the initial treatment of femoral acetabular syndrome, it is important to have clear and accurate communication with all members of the treatment team, including the physical therapist, patient, other clinicians, coach and trainer, if appropriate. If surgical options are explored it is also important to communicate with orthopedic physicians for post-operative rehabilitation planning.

Patient & family education

Special emphasis should be placed on patient and primary care provider education since FAI is an uncommon condition.

Patients should be educated as part of the treatment plan, including avoiding exacerbating/impingement positions, home exercises, and return to play.

Outcome Measures

No specific outcome measures for FAI have been developed, but pain and function should be followed during treatment. Validated questionnaires for patients with hip or groin pain and for assessment of perceived quality of life and general health status are useful for evaluation of patients with FAI syndrome.

Emerging Interventions

Regenerative medicine for symptomatic relief and to delay surgical management has been considered in the literature, but scientific data to support their use in FAI syndrome is insufficient.

Translation into practice: practice “pearls”/changes in clinical practice behaviors and skills

Adequate recognition of the symptomatology, clinical signs and imaging findings for FAI syndrome is key in differentiating FAI syndrome from other pain syndromes. Delayed diagnosis may cause functional impairments, degenerative changes of the hip joint and leads to unnecessary imaging studies and interventions.


Cutting edge concepts and practice

It is necessary to know the proper nomenclature to diagnose FAI syndrome. The triad of symptoms, clinical signs and imaging findings must be fulfilled. Positive imaging findings in the absence symptoms or clinical signs are called cam-morphology or pincer-morphology, but the terms pincer-impingement or cam-impingement should be avoided to prevent ambiguity in medical taxonomy.


Gaps in the evidence-based knowledge

Better understanding of morphologic development, how sporting activities in the childhood influences FAI syndrome, possible triggers for symptom development, the utility of diagnostic criteria and the long-term natural history of the disorder are targets for investigation. Randomized controlled trials are needed to determine benefits and safeness of treatment strategies and to compare their effectiveness.


  1. Griffin DR, Dickenson EJ, O’Donnell JM, et al. Infographic. The Warwick Agreement on femoroacetabular impingement syndrome (FAI syndrome): an international consensus statement. Br J Sports Med 2016;50:1169–76.
  2. Parvizi J, Leunig M, Ganz R. Femoroacetabular impingement. JAAOS. 2007;15:561-570.
  3. Kaplan KM, Shah M, Youm T. Femoroacetabular impingement: diagnosis and treatment. Bulletin of the NYU Hosp for Joint Diseases. 2010;68:70-75.
  4. Martin DE, Tashman S. The biomechanics of femoroacetabular impingement. Operative Techniques in Orthopaedics. 2010;20(4):248–254.
  5. Field RE, Rajakulendran K. The labro-acetabular complex. Bone Jt. Surg. (Am). 2011;93 Suppl 2:22-27.
  6. Tannast M, Siebenrock KA, Anderson SE. Femoroacetabular impingement: radiographic diagnosis—what the radiologist should know. AJR Am J Roentgenol 2007;188:1540–52.
  7. Sankar WN, Nevitt M, Parvizi J, et al. Femoroacetabular impingement: defining the condition and its role in the pathophysiology of osteoarthritis. J Am Acad Orthop Surg 2013;21(Suppl 1):S7–S15.
  8. Imam S, Khanduja V. Current concepts in the diagnosis and management of femoroacetabular impingement. International Orthopaedics. 2011;35:1427-1435.
  9. Macfarlane RJ, Haddad F. The diagnosis and management of femoro-acetabular impingement. Annals of RCS England. 2010;92:363-367.
  10. Mauro CSV, James E, Kelly BT. Femoroacetabular impingement surgical techniques. Operative Techniques in Othropaedics. 2010;20:223-230.
  11. Emara K, Samir W, Motasem el H, Ghafar K. Conservative treatment for mild femoroacetabular impingement. J Orthop Surg (Hong Kong) 2011;19:41-45.
  12. Ejnisman L, Philippon M, Lertwanich P. Femoroacetabular impingement: the femoral side. Clinics in Sports Medicine. 2011;30:369-377.
  13. Beck M, Kalhor M, Leunig M, Ganz R. Hip morphology influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip. Bone Jt. Surg. (Brit). 2005;87:1012-1018.
  14. Ganz R, Parvizi J, Beck M, et al. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res 2003;417:112–20.
  15. Philippon MJ, Maxwell R, Johnston T, Schenker M, Briggs K. Clinical presentation of femoroacetabular impingement. Knee Surgery, Sports Traumatology, Arthroscopy. 2007;15:1041-1047.
  16. Manaster BJ, Zakel S. Imaging of femoral acetabular impingement syndrome. Clinics in Sports Medicine. 2006;25:635-657.
  17. Agricola R, Waarsing JH, Arden NK, et al. Cam impingement of the hip: a risk factor for hip osteoarthritis. Nat Rev Rheumatol 2013;9:630–4.
  18. Martin HD, Palmer IJ. History and physical examination of the hip: the basics. Curr Rev Musculoskelet Med 2013;6:219–25.
  19. Wall PD, Brown JS, Parsons N, et al. Surgery for treating hip impingement (femoroacetabular impingement). The Cochrane Library, 2014.
  20. Wall PD, Fernandez M, Griffin DR, et al. Nonoperative treatment for femoroacetabular impingement: a systematic review of the literature. PM R 2013;5:418–26.

Original Version of the Topic

Mark L. Miedema, MD and Ryan O. Stephenson, DO. Femoral acetabular syndrome. 12/28/2012.

Author Disclosure

Fernando Sepulveda, MD
Nothing to Disclose

Belmarie Rodriguez, DO
Nothing to Disclose