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What is femoroacetabular impingement?
  1. R Agricola1,
  2. H Weinans2,3
  1. 1Department of Orthopaedic Surgery, Erasmus University Medical Center, Rotterdam, The Netherlands
  2. 2Departments of Orthopaedic Surgery and Rheumatology, University Medical Center Utrecht, Utrecht, The Netherlands
  3. 3Department of Biomechanical Engineering, Technical University Delft, Delft, The Netherlands
  1. Correspondence to R Agricola, Department of Orthopaedic Surgery, Erasmus University Medical Center, dr Molewaterplein 50, Room EE16-14, Rotterdam 3015GE, The Netherlands; r.agricola{at}

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Definition of femoroacetabular impingement (FAI)

Femoroacetabular impingement (FAI) has gained much attention over the past decade. It has been associated with hip and groin pain, decreased hip function and can ultimately lead to osteoarthritis.1 A recent consensus meeting defined FAI as “a clinical entity in which a pathological mechanical process causes hip pain when morphological abnormalities of the acetabulum and/or femur, combined with vigorous hip motion (especially at the extremes), lead to repetitive collisions that damage the soft-tissue structures within the joint itself.”2 However, there is a lack of clarity regarding the definition of morphological abnormalities.

Distinguishing between normal and abnormal morphology

The presence of a cam or pincer deformity is a prerequisite for defining cam-type and pincer-type of FAI. Although an obvious cam deformity is not difficult to recognise, there may be subtle differences between normal and abnormal bony morphology. This is illustrated by a study showing poor correlation between the subjective assessment of the head–neck junction and objective measures.3 Poor reliability of radiologists and orthopaedic surgeons in quantifying morphological abnormalities has also been demonstrated.4 Objective methods to quantify a cam deformity are, therefore, preferable. Several …

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  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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