Plain radiograph of crossover sign for femoroacetabular impingement

AP view of the right hip. The anterior (open dots) and posterior (solid dots) rim of the acetabulum are marked. The superior portion of the anterior rim lies lateral to the posterior rim (arrow) indicating overcoverage of the acetabulum. Anteriorly, it assumes a more normal medial position, creating the crossover sign (arrowhead), which is an indicator of a pincer-type femoroacetabular impingement.