Expert Opinion and Controversies in Musculoskeletal and Sports Medicine: Femoroacetabular Impingement

Depictions of hip morphology and motion in the setting of a normal hip (top), pincer impingement (middle), and cam impingement (bottom). In pincer impingement, note that the acetabulum is deep, with overcoverage of the femoral head. In full flexion, there is contact between the femoral neck and the acetabular rim accompanied by posteroinferior joint subluxation. In cam impingement, an abnormality at the femoral head-neck junction is forced into the acetabular rim in full hip flexion. Reprinted with permission.^8(p1541)

Radiographic appearance of the right hip on an anteroposterior view. (A) A normal hip. The acetabular fossa (F) is lateral to the ilioischial line (IIL), and the acetabulum does not completely cover the femoral head (E). The arc of the epiphyseal scar (arrows) lies within the circular contour of the femoral head. (B) Pincer impingement. Overcoverage of the femoral head by the acetabulum is present. Acetabular retroversion is depicted, defined by the anterior wall (AW) of the acetabulum being more lateral than the posterior wall (PW). The anterior wall lies medial to the posterior wall in a normal hip. (C) Cam impingement. Note that the epiphyseal scar (arrows) has an abnormal lateral extension that results in an aspherical femoral head and alters the appearance of the femoral head-neck junction (so-called pistol grip deformity). Reprinted with permission.^{8(p1544,1545,1548)}