Fig. 1

(A) In a normal hip, the acetabulum sufficiently covers the femoral head. (B) In coxa profunda, the head is more medial with the acetabular fossa being at or medial to the ilioischial line. (C) In protrusio, the femoral head is close, at or medial to the ilioischial line and the acetabular roof is negatively tilted with the center of the femoral head being medial to the anterior and posterior acetabular walls. (Reprinted with permission from Leunig, M., Huff, T., Ganz, R. Femoroacetabular impingement: Treatment of the acetabular side. In: Azar FM, O’Connor MI (eds). Instructional Course Lectures 58. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2009:223–229.)