Femoroacetabular impingement

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Femoroacetabular impingement
The three recognized types of femoroacetabular impingement. Click image to see video illustration of the three types.

Femoroacetabular Impingement (FAI), or hip impingement syndrome, is a condition involving one or more anatomical abnormalities of the hip joint, which is a ball and socket joint.[1] It is a common cause of hip pain and discomfort in young and middle-aged adults.[2] It occurs when the ball shaped femoral head contacts the acetabulum abnormally or does not permit a normal range of motion in the acetabular socket.[3] Damage can occur to the articular cartilage, or labral cartilage (soft tissue, ring-shaped bumper of the socket), or both.[4] The condition may be symptomatic or asymptomatic and has been found to be a cause of osteoarthritis of the hip.[1] Treatment options range from conservative management to surgery.[5]

Signs and symptoms[edit]

Pain is the most common complaint in those with FAI.[6] It is experienced in a number of areas, making the diagnosis challenging, but commonly occurs in the groin, upper buttock/lower back, the buttock or beneath the buttock, side of the affected hip and posterior upper leg.[6][3][7] Onset of symptoms has been reported to present in both an acute and more gradual manner.[6] Aggravating symptoms that are commonly reported include repetitive or prolonged squatting, twisting movements of the hip, like pivoting during athletics, and even sitting for prolonged periods.[6][8] Pain while getting in and out of cars has also been reported.[8] The pain is often significant enough to cause a decrease in activity level and movement.[6] Some will also describe decreased range of motion of the affected hip.[9]


FAI is characterized by abnormal contact between the proximal femur and rim of the acetabulum (hip socket). In most cases, patients present with a deformity in the femoral head, or acetabulum, a poorly positioned femoral-acetabular junction, or any or all of the foregoing.[3] The cause of FAI is currently unknown, but both congenital and acquired etiologies have been put forth. Studies have shown an increased incidence in siblings, suggesting a genetic component.[10] At least one study has also shown a predilection in the Caucasian population.[10] It has also been reported to be more common in males.[10] However, there is no concrete evidence to suggest a genetic trait and instead, the most favored theory currently supports that FAI (the cam type in particular) is due to repetitive movements involving the hip (e.g. squatting) in young athletes.[10] A combination of these factors may also predispose to a form of FAI; predominantly, a marginal developmental hip abnormality together with environmental factors such as recurrent motion of the legs within a supraphysiologic range.[11]

Three types of FAI are recognized (see title image). The first involves an excess of bone along the upper surface of the femoral head, known as a cam deformity (abbreviation for camshaft, which the shape of the femoral head and neck resembles). The second is due to an excess of growth of the upper lip of the acetabular cup and is known as a 'pincer' deformity. The third is a combination of the two, generally referred to as 'mixed.' The most common type seen, approximately 70% of the time, is the mixed type.[12] A complicating issue is that some of the radiographic findings of FAI have also been described in asymptomatic subjects.[13]

Current literature suggests that the cam type of impingement is associated with the development of hip osteoarthritis.[14] Thus far, no correlation has been seen between the pincer type and development of hip osteoarthritis.[14]


Radiograph of a cam type impingement.
Radiograph of a pincer type impingement.

Clinical evaluation is the first step in diagnosis, but will rarely lead to the diagnosis on its own, due to inconsistent and vague nature of the pain.[10] Childhood and current activity should be inquired about. Physical exam should also involve assessing passive internal rotation of the hip during flexion, as range of motion is reduced in proportion to the size of a cam lesion.[10] Flexing the hip to 90 degrees, adducting, and internally rotating the hip, known as the FADDIR test, should also be performed.[10] It is positive when it causes pain.

Radiographic assessment is often considered first line for FAI, providing a two-dimensional view of the hip joints.[10] Anterior-posterior pelvis and a lateral image of the hip in question should be attained.[10] A 45-degree Dunn view is also recommended.[10][15] MRI imaging may follow, particularly if there is no specific evidence on radiographs, producing a three-dimensional reconstruction of the joint for better definition, to evaluate the hip cartilage, or measure hip socket angles (e.g. the alpha-angle as described by Nötzli[16] in 2-D and by Siebenrock in 3-D[17]). MR arthrogram had been used in the past, as it was more sensitive for picking up soft tissue lesions; however, due to improvement in technology, MRI is now considered comparable for picking up such lesions.[6] CT is not usually used due to radiation exposure and no benefit above MRI.[6] It is possible to perform dynamic simulation of hip motion with CT or MRI[18][19] assisting to establish whether, where, and to what extent, impingement is occurring.

The diagnosis is often made in conjunction with a labral tear.[20]

Differential Diagnosis[9][edit]


Prevention is currently being investigated.[21] The goal of prevention would be to avoid joint damage and premature hip osteoarthritis.[21] Studies are examining the effectiveness of screening adolescents in school and targeting at-risk individuals for education, physical therapy and decreasing participation in possibly harmful activities/sports.[21]


Treatment of FAI can divided into those that are non-operative (conservative) and operative. Conservative treatment is often prescribed for those who have not yet received any therapy.[22] Conservative treatment includes physical therapy, avoidance of those activities that produce pain, and nonsteroidal anti-inflammatory drugs.[6] It may also include joint injections with cortisone or hyaluronic acid, particularly for those who wish to avoid surgery.[6]

Physical therapy is implemented for the purpose of improving joint mobility, strengthening muscles surrounding the joint, correcting posture, and treating any other muscle or joint deficits that may be exacerbating the condition.[8] A movement analysis may also be performed to identify specific movement patterns that may be causing injury.[23] It should be noted, however, that studies to demonstrate the effectiveness of physical therapy are currently underway, with no conclusive results to date.[22]

Operative treatment is generally recommended to those who continue to have symptoms. It involves the surgical correction of any bony abnormalities causing the impingement and correction of any soft tissue lesions, such as labral tears.[6] The primary aim of surgery is to correct the fit of the femoral head and acetabulum to create a hip socket that reduces contact between the two, allowing a greater range of movement.[24] This includes femoral head sculpting and/or trimming of the acetabular rim.[24][25]

Surgery may be arthroscopic or open.[7] A 2011 study analyzing current surgical methods for management of symptomatic femoral acetabular impingement, suggested that the arthroscopic method had surgical outcomes equal to or better than other methods with a lower rate of major complications when performed by experienced surgeons;[26] consequently, the surgery is now rarely done open.[27]

Outcomes of arthroscopic surgery are currently being studied, but have generally been positive. When performed on elite athletes, most are able to return their previous level of competition.[10]

Long term, randomized controlled trials evaluating the efficacy of conservative and operative treatments are underway.[28]


FAI is a relatively recent discovery. It's original description is credited to orthopedic surgeon Dr. Reinhold Ganz, who first proposed the condition as a cause for hip osteoarthritis in a publication in 2003.[29][30]


Notable persons who have suffered hip impingement:


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  7. ^ a b Chakraverty, J.K.; Snelling, N.J. (2012). "Anterior hip pain – Have you considered femoroacetabular impingement?". International Journal of Osteopathic Medicine. 15: 22. doi:10.1016/j.ijosm.2011.09.003.
  8. ^ a b c Kuhlman GS, Domb BG (December 2009). "Hip impingement: identifying and treating a common cause of hip pain". American Family Physician. 80 (12): 1429–34. PMID 20000305.
  9. ^ a b Ghaffari A, Davis I, Storey T, Moser M (November 2018). "Current Concepts of Femoroacetabular Impingement". Radiologic Clinics of North America. 56 (6): 965–982. doi:10.1016/j.rcl.2018.06.009. PMID 30322493.
  10. ^ a b c d e f g h i j k Egger, Anthony C.; Frangiamore, Salvatore; Rosneck, James (Dec 2016). "Femoroacetabular Impingement: A Review". Sports Medicine and Arthroscopy Review. 24 (4): e53–e58. doi:10.1097/JSA.0000000000000126. ISSN 1538-1951. PMID 27811519.
  11. ^ Leunig M, Beaulé PE, Ganz R (March 2009). "The concept of femoroacetabular impingement: current status and future perspectives". Clinical Orthopaedics and Related Research. 467 (3): 616–22. doi:10.1007/s11999-008-0646-0. PMC 2635437. PMID 19082681.
  12. ^ Beck M, Kalhor M, Leunig M, Ganz R (July 2005). "Hip morphology influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip". The Journal of Bone and Joint Surgery. British Volume. 87 (7): 1012–8. doi:10.1302/0301-620X.87B7.15203. PMID 15972923.
  13. ^ Chakraverty JK, Sullivan C, Gan C, Narayanaswamy S, Kamath S (February 2013). "Cam and pincer femoroacetabular impingement: CT findings of features resembling femoroacetabular impingement in a young population without symptoms". AJR. American Journal of Roentgenology. 200 (2): 389–95. doi:10.2214/AJR.12.8546. PMID 23345362.
  14. ^ a b van Klij, Pim; Heerey, Joshua; Waarsing, Jan H.; Agricola, Rintje (April 2018). "The Prevalence of Cam and Pincer Morphology and Its Association With Development of Hip Osteoarthritis". The Journal of Orthopaedic and Sports Physical Therapy. 48 (4): 230–238. doi:10.2519/jospt.2018.7816. ISSN 1938-1344. PMID 29548271.
  15. ^ Clohisy JC, Carlisle JC, Beaulé PE, Kim YJ, Trousdale RT, Sierra RJ, Leunig M, Schoenecker PL, Millis MB (November 2008). "A systematic approach to the plain radiographic evaluation of the young adult hip". The Journal of Bone and Joint Surgery. American Volume. 90 Suppl 4: 47–66. doi:10.2106/JBJS.H.00756. PMC 2682767. PMID 18984718.
  16. ^ Nötzli HP, Wyss TF, Stoecklin CH, Schmid MR, Treiber K, Hodler J (May 2002). "The contour of the femoral head-neck junction as a predictor for the risk of anterior impingement". The Journal of Bone and Joint Surgery. British Volume. 84 (4): 556–60. doi:10.1302/0301-620X.84B4.12014. PMID 12043778.
  17. ^ Siebenrock KA, Ferner F, Noble PC, Santore RF, Werlen S, Mamisch TC (November 2011). "The cam-type deformity of the proximal femur arises in childhood in response to vigorous sporting activity". Clinical Orthopaedics and Related Research. 469 (11): 3229–40. doi:10.1007/s11999-011-1945-4. PMC 3183218. PMID 21761254.
  18. ^ Tannast M, Kubiak-Langer M, Langlotz F, Puls M, Murphy SB, Siebenrock KA (January 2007). "Noninvasive three-dimensional assessment of femoroacetabular impingement". Journal of Orthopaedic Research. 25 (1): 122–31. doi:10.1002/jor.20309. PMID 17054112.
  19. ^ http://www.clinicalgraphics.com Dynamic motion simulation for hip impingement.
  20. ^ Bedi, A., Chen, N., Robertson, W., & Kelly, B. T. (2008). The management of labral tears and femoroacetabular impingement of the hip in the young, active patient. Arthroscopy: The Journal of Arthroscopic & Related Surgery, 24(10), 1135-1145.
  21. ^ a b c Cakic, J.; Patricios, J. (July 2014). "Femoroacetabular impingement: prevention or intervention? The sports physician's quandary". British Journal of Sports Medicine. 48 (14): 1073–1074. doi:10.1136/bjsports-2014-093792. ISSN 1473-0480. PMID 24858362.
  22. ^ a b Casartelli, Nicola C.; Bizzini, Mario; Kemp, Joanne; Naal, Florian D.; Leunig, Michael; Maffiuletti, Nicola A. (May 2018). "What treatment options exist for patients with femoroacetabular impingement syndrome but without surgical indication?". British Journal of Sports Medicine. 52 (9): 552–553. doi:10.1136/bjsports-2017-098059. ISSN 1473-0480. PMID 28935688.
  23. ^ Loudon, Janice K.; Reiman, Michael P. (May 2014). "Conservative management of femoroacetabular impingement (FAI) in the long distance runner". Physical Therapy in Sport: Official Journal of the Association of Chartered Physiotherapists in Sports Medicine. 15 (2): 82–90. doi:10.1016/j.ptsp.2014.02.004. ISSN 1873-1600. PMID 24629576.
  24. ^ a b "Bone & Joint". online.boneandjoint.org.uk. doi:10.1302/2058-5241.3.170041. PMC 5941972. PMID 29780619. Retrieved 2019-01-22.
  25. ^ Bhatia, Sanjeev; Lee, Simon; Shewman, Elizabeth; Mather, Richard C.; Salata, Michael J.; Bush-Joseph, Charles A.; Nho, Shane J. (Sep 2015). "Effects of acetabular rim trimming on hip joint contact pressures: how much is too much?". The American Journal of Sports Medicine. 43 (9): 2138–2145. doi:10.1177/0363546515590400. ISSN 1552-3365. PMID 26180260.
  26. ^ Matsuda DK, Carlisle JC, Arthurs SC, Wierks CH, Philippon MJ (February 2011). "Comparative systematic review of the open dislocation, mini-open, and arthroscopic surgeries for femoroacetabular impingement". Arthroscopy. 27 (2): 252–69. doi:10.1016/j.arthro.2010.09.011. PMID 21266276.
  27. ^ Kierkegaard, Signe; Langeskov-Christensen, Martin; Lund, Bent; Naal, Florian D.; Mechlenburg, Inger; Dalgas, Ulrik; Casartelli, Nicola C. (April 2017). "Pain, activities of daily living and sport function at different time points after hip arthroscopy in patients with femoroacetabular impingement: a systematic review with meta-analysis". British Journal of Sports Medicine. 51 (7): 572–579. doi:10.1136/bjsports-2016-096618. ISSN 1473-0480. PMID 27845683.
  28. ^ Wall PD, Brown JS, Parsons N, Buchbinder R, Costa ML, Griffin D (September 2014). "Surgery for treating hip impingement (femoroacetabular impingement)". The Cochrane Database of Systematic Reviews. 9 (9): CD010796. doi:10.1002/14651858.CD010796.pub2. PMID 25198064.
  29. ^ a b c d Hessel, Joy A. (May 2014). "Femoroacetabular impingement in athletes". Orthopedic Nursing. 33 (3): 137–139, quiz 140–141. doi:10.1097/NOR.0000000000000045. ISSN 1542-538X. PMID 24845836.
  30. ^ Ganz, Reinhold; Parvizi, Javad; Beck, Martin; Leunig, Michael; Nötzli, Hubert; Siebenrock, Klaus A. (Dec 2003). "Femoroacetabular impingement: a cause for osteoarthritis of the hip". Clinical Orthopaedics and Related Research (417): 112–120. doi:10.1097/01.blo.0000096804.78689.c2. ISSN 0009-921X. PMID 14646708.
  31. ^ "Hip issue lands struggling Cardinals reliever Holland on DL". AP NEWS. 2018-05-26. Retrieved 2019-01-19.
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  34. ^ http://www.nba.com/celtics/news/press-052017-isaiah-thomas-ruled-out-for-game-3
  35. ^ Marston, Robert (2018-01-02). "Medical opinion: Andy Murray may have degenerative arthritis, leaving hip replacement as the likely optionÂ". The Telegraph. ISSN 0307-1235. Retrieved 2019-01-19.

Further reading[edit]

External links[edit]