Bump at anterolateral femoral head-neck junction: may result from eccentric skeletal maturation
Flat anterosuperior femoral head-neck junction: may reflect subclinical slipped capital femoral epiphysis
Primarily young men
Pincer type: prominence of anterior acetabulum leads to impingement on femoral neck
Coxa profunda: acetabulum too deep with excessive surface area
Posterior acetabular deficiency: femoral head shifts posteriorly with hip flexion, increasing coverage by acetabulum anteriorly
Primarily middle-aged women
May have both cam and pincer FAI in same patient
Most common morphology is combined
IMAGING
General Features
Radiographic Findings
MR Findings
Imaging Recommendations
Pitfalls
DIFFERENTIAL DIAGNOSIS
PATHOLOGY
General Features
Staging, Grading, & Classification
Gross Pathologic & Surgical Features
Microscopic Features
CLINICAL ISSUES
Presentation
Natural History & Prognosis
Treatment
DIAGNOSTIC CHECKLIST
Consider
Image Interpretation Pearls
Reporting Tips
Selected References
Welton KL et al: The anteroposterior pelvic radiograph: acetabular and femoral measurements and relation to hip pathologies. J Bone Joint Surg Am. 100(1):76-85, 2018
Petersen BD et al: Lateral acetabular labral length is inversely related to acetabular coverage as measured by lateral center edge angle of Wiberg. J Hip Preserv Surg. 3(3):190-6, 2016
Sutter R et al: Assessment of femoral antetorsion with MRI: comparison of oblique measurements to standard transverse measurements. AJR Am J Roentgenol. 205(1):130-5, 2015
Byrd JW: Femoroacetabular impingement in athletes: current concepts. Am J Sports Med. 42(3):737-51, 2014
Lepage-Saucier M et al: Femoroacetabular impingement: normal values of the quantitative morphometric parameters in asymptomatic hips. Eur Radiol. 24(7):1707-14, 2014
Omoumi P et al: Anatomic features associated with femoroacetabular impingement are equally common in hips of old and young asymptomatic individuals without CT signs of osteoarthritis. AJR Am J Roentgenol. 202(5):1078-86, 2014
Riley GM et al: MRI of the hip for the evaluation of femoroacetabular impingement; past, present, and future. J Magn Reson Imaging. 41(3):558-72, 2014
Tranovich MJ et al: A review of femoroacetabular impingement and hip arthroscopy in the athlete. Phys Sportsmed. 42(1):75-87, 2014
Bredella MA et al: Femoroacetabular impingement. Magn Reson Imaging Clin N Am. 21(1):45-64, 2013
Dimmick S et al: Femoroacetabular impingement. Radiol Clin North Am. 51(3):337-52, 2013
Nepple JJ et al: Coxa profunda is not a useful radiographic parameter for diagnosing pincer-type femoroacetabular impingement. J Bone Joint Surg Am. 95(5):417-23, 2013
Petchprapa CN et al: Imaging of chondral lesions including femoroacetabular impingement. Semin Musculoskelet Radiol. 17(3):258-71, 2013
Philippon MJ et al: Prevalence of increased alpha angles as a measure of cam-type femoroacetabular impingement in youth ice hockey players. Am J Sports Med. 41(6):1357-62, 2013
Rubin DA: Femoroacetabular impingement: fact, fiction, or fantasy? AJR Am J Roentgenol. 201(3):526-34, 2013
Sankar WN et al: Femoroacetabular impingement: current concepts and controversies. Orthop Clin North Am. 44(4):575-89, 2013
Schmitz MR et al: Spectrum of radiographic femoroacetabular impingement morphology in adolescents and young adults: an EOS-based double-cohort study. J Bone Joint Surg Am. 95(13):e90, 2013
Larson CM et al: Arthroscopic debridement versus refixation of the acetabular labrum associated with femoroacetabular impingement: mean 3.5-year follow-up. Am J Sports Med. 40(5):1015-21, 2012
Robinson P: Conventional 3-T MRI and 1.5-T MR arthrography of femoroacetabular impingement. AJR Am J Roentgenol. 199(3):509-15, 2012
Sutter R et al: Femoral antetorsion: comparing asymptomatic volunteers and patients with femoroacetabular impingement. Radiology. 263(2):475-83, 2012
Sutter R et al: How useful is the alpha angle for discriminating between symptomatic patients with cam-type femoroacetabular impingement and asymptomatic volunteers? Radiology. 264(2):514-21, 2012
Banerjee P et al: Femoroacetabular impingement: a review of diagnosis and management. Curr Rev Musculoskelet Med. 4(1):23-32, 2011
Laborie LB et al: Prevalence of radiographic findings thought to be associated with femoroacetabular impingement in a population-based cohort of 2081 healthy young adults. Radiology. 260(2):494-502, 2011
Palmer WE: Femoroacetabular impingement: caution is warranted in making imaging-based assumptions and diagnoses. Radiology. 257(1):4-7, 2010
Jessel RH et al: Radiographic and patient factors associated with pre-radiographic osteoarthritis in hip dysplasia. J Bone Joint Surg Am. 91(5):1120-9, 2009
Kang C et al: Acetabular labral tears in patients with sports injury. Clin Orthop Surg. 1(4):230-5, 2009
Leunig M et al: The concept of femoroacetabular impingement: current status and future perspectives. Clin Orthop Relat Res. 467(3):616-22, 2009
Lohan DG et al: Cam-type femoral-acetabular impingement: is the alpha angle the best MR arthrography has to offer? Skeletal Radiol. 38(9):855-62, 2009
Pfirrmann CW et al: MR arthrography of acetabular cartilage delamination in femoroacetabular cam impingement. Radiology. 249(1):236-41, 2008
Tannast M et al: Femoroacetabular impingement: radiographic diagnosis--what the radiologist should know. AJR Am J Roentgenol. 188(6):1540-52, 2007
Blankenbaker DG et al: The painful hip: new concepts. Skeletal Radiol. 35(6):352-70, 2006
Martinez AE et al: Os acetabuli in femoro-acetabular impingement: stress fracture or unfused secondary ossification centre of the acetabular rim? Hip Int. 16(4):281-6, 2006
Bredella MA et al: MR imaging of femoroacetabular impingement. Magn Reson Imaging Clin N Am. 13(4):653-64, 2005
Kassarjian A et al: Triad of MR arthrographic findings in patients with cam-type femoroacetabular impingement. Radiology. 236(2):588-92, 2005
Siebenrock KA et al: Anterior femoro-acetabular impingement due to acetabular retroversion. Treatment with periacetabular osteotomy. J Bone Joint Surg Am. 85-A(2):278-86, 2003
Ito K et al: Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset. J Bone Joint Surg Br. 83(2):171-6, 2001
Abe I et al: Acetabular labrum: abnormal findings at MR imaging in asymptomatic hips. Radiology. 216(2):576-81, 2000
Ferguson SJ et al: The influence of the acetabular labrum on hip joint cartilage consolidation: a poroelastic finite element model. J Biomech. 33(8):953-60, 2000
Myers SR et al: Anterior femoroacetabular impingement after periacetabular osteotomy. Clin Orthop Relat Res. (363):93-9, 1999
Tönnis D et al: Acetabular and femoral anteversion: relationship with osteoarthritis of the hip. J Bone Joint Surg Am. 81(12):1747-70, 1999
Related Anatomy
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Related Differential Diagnoses
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References
Tables
Tables
KEY FACTS
Terminology
Imaging
Pathology
Clinical Issues
Diagnostic Checklist
TERMINOLOGY
Abbreviations
Femoral acetabular impingement (FAI)
Definitions
Morphologic abnormality at femoral head-neck junction or acetabulum resulting in osseous &/or labral and cartilaginous impingement
Cam type: prominence at femoral head-neck junction impinges anterosuperior acetabulum
Bump at anterolateral femoral head-neck junction: may result from eccentric skeletal maturation
Flat anterosuperior femoral head-neck junction: may reflect subclinical slipped capital femoral epiphysis
Primarily young men
Pincer type: prominence of anterior acetabulum leads to impingement on femoral neck
Coxa profunda: acetabulum too deep with excessive surface area
Posterior acetabular deficiency: femoral head shifts posteriorly with hip flexion, increasing coverage by acetabulum anteriorly
Primarily middle-aged women
May have both cam and pincer FAI in same patient
Most common morphology is combined
IMAGING
General Features
Radiographic Findings
MR Findings
Imaging Recommendations
Pitfalls
DIFFERENTIAL DIAGNOSIS
PATHOLOGY
General Features
Staging, Grading, & Classification
Gross Pathologic & Surgical Features
Microscopic Features
CLINICAL ISSUES
Presentation
Natural History & Prognosis
Treatment
DIAGNOSTIC CHECKLIST
Consider
Image Interpretation Pearls
Reporting Tips
Selected References
Welton KL et al: The anteroposterior pelvic radiograph: acetabular and femoral measurements and relation to hip pathologies. J Bone Joint Surg Am. 100(1):76-85, 2018
Petersen BD et al: Lateral acetabular labral length is inversely related to acetabular coverage as measured by lateral center edge angle of Wiberg. J Hip Preserv Surg. 3(3):190-6, 2016
Sutter R et al: Assessment of femoral antetorsion with MRI: comparison of oblique measurements to standard transverse measurements. AJR Am J Roentgenol. 205(1):130-5, 2015
Byrd JW: Femoroacetabular impingement in athletes: current concepts. Am J Sports Med. 42(3):737-51, 2014
Lepage-Saucier M et al: Femoroacetabular impingement: normal values of the quantitative morphometric parameters in asymptomatic hips. Eur Radiol. 24(7):1707-14, 2014
Omoumi P et al: Anatomic features associated with femoroacetabular impingement are equally common in hips of old and young asymptomatic individuals without CT signs of osteoarthritis. AJR Am J Roentgenol. 202(5):1078-86, 2014
Riley GM et al: MRI of the hip for the evaluation of femoroacetabular impingement; past, present, and future. J Magn Reson Imaging. 41(3):558-72, 2014
Tranovich MJ et al: A review of femoroacetabular impingement and hip arthroscopy in the athlete. Phys Sportsmed. 42(1):75-87, 2014
Bredella MA et al: Femoroacetabular impingement. Magn Reson Imaging Clin N Am. 21(1):45-64, 2013
Dimmick S et al: Femoroacetabular impingement. Radiol Clin North Am. 51(3):337-52, 2013
Nepple JJ et al: Coxa profunda is not a useful radiographic parameter for diagnosing pincer-type femoroacetabular impingement. J Bone Joint Surg Am. 95(5):417-23, 2013
Petchprapa CN et al: Imaging of chondral lesions including femoroacetabular impingement. Semin Musculoskelet Radiol. 17(3):258-71, 2013
Philippon MJ et al: Prevalence of increased alpha angles as a measure of cam-type femoroacetabular impingement in youth ice hockey players. Am J Sports Med. 41(6):1357-62, 2013
Rubin DA: Femoroacetabular impingement: fact, fiction, or fantasy? AJR Am J Roentgenol. 201(3):526-34, 2013
Sankar WN et al: Femoroacetabular impingement: current concepts and controversies. Orthop Clin North Am. 44(4):575-89, 2013
Schmitz MR et al: Spectrum of radiographic femoroacetabular impingement morphology in adolescents and young adults: an EOS-based double-cohort study. J Bone Joint Surg Am. 95(13):e90, 2013
Larson CM et al: Arthroscopic debridement versus refixation of the acetabular labrum associated with femoroacetabular impingement: mean 3.5-year follow-up. Am J Sports Med. 40(5):1015-21, 2012
Robinson P: Conventional 3-T MRI and 1.5-T MR arthrography of femoroacetabular impingement. AJR Am J Roentgenol. 199(3):509-15, 2012
Sutter R et al: Femoral antetorsion: comparing asymptomatic volunteers and patients with femoroacetabular impingement. Radiology. 263(2):475-83, 2012
Sutter R et al: How useful is the alpha angle for discriminating between symptomatic patients with cam-type femoroacetabular impingement and asymptomatic volunteers? Radiology. 264(2):514-21, 2012
Banerjee P et al: Femoroacetabular impingement: a review of diagnosis and management. Curr Rev Musculoskelet Med. 4(1):23-32, 2011
Laborie LB et al: Prevalence of radiographic findings thought to be associated with femoroacetabular impingement in a population-based cohort of 2081 healthy young adults. Radiology. 260(2):494-502, 2011
Palmer WE: Femoroacetabular impingement: caution is warranted in making imaging-based assumptions and diagnoses. Radiology. 257(1):4-7, 2010
Jessel RH et al: Radiographic and patient factors associated with pre-radiographic osteoarthritis in hip dysplasia. J Bone Joint Surg Am. 91(5):1120-9, 2009
Kang C et al: Acetabular labral tears in patients with sports injury. Clin Orthop Surg. 1(4):230-5, 2009
Leunig M et al: The concept of femoroacetabular impingement: current status and future perspectives. Clin Orthop Relat Res. 467(3):616-22, 2009
Lohan DG et al: Cam-type femoral-acetabular impingement: is the alpha angle the best MR arthrography has to offer? Skeletal Radiol. 38(9):855-62, 2009
Pfirrmann CW et al: MR arthrography of acetabular cartilage delamination in femoroacetabular cam impingement. Radiology. 249(1):236-41, 2008
Tannast M et al: Femoroacetabular impingement: radiographic diagnosis--what the radiologist should know. AJR Am J Roentgenol. 188(6):1540-52, 2007
Blankenbaker DG et al: The painful hip: new concepts. Skeletal Radiol. 35(6):352-70, 2006
Martinez AE et al: Os acetabuli in femoro-acetabular impingement: stress fracture or unfused secondary ossification centre of the acetabular rim? Hip Int. 16(4):281-6, 2006
Bredella MA et al: MR imaging of femoroacetabular impingement. Magn Reson Imaging Clin N Am. 13(4):653-64, 2005
Kassarjian A et al: Triad of MR arthrographic findings in patients with cam-type femoroacetabular impingement. Radiology. 236(2):588-92, 2005
Siebenrock KA et al: Anterior femoro-acetabular impingement due to acetabular retroversion. Treatment with periacetabular osteotomy. J Bone Joint Surg Am. 85-A(2):278-86, 2003
Ito K et al: Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset. J Bone Joint Surg Br. 83(2):171-6, 2001
Abe I et al: Acetabular labrum: abnormal findings at MR imaging in asymptomatic hips. Radiology. 216(2):576-81, 2000
Ferguson SJ et al: The influence of the acetabular labrum on hip joint cartilage consolidation: a poroelastic finite element model. J Biomech. 33(8):953-60, 2000
Myers SR et al: Anterior femoroacetabular impingement after periacetabular osteotomy. Clin Orthop Relat Res. (363):93-9, 1999
Tönnis D et al: Acetabular and femoral anteversion: relationship with osteoarthritis of the hip. J Bone Joint Surg Am. 81(12):1747-70, 1999
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