Solution: Femoroacetabular impingement syndrome is a significant cause of early osteoarthritis in the hip. Two types of impingement are identified: Pincer impingement is characterized by focal or general overcoverage of the femoral head by the acetabulum and cam impingement is due to an aspherical portion of the femoral head–neck junction, as is seen in this case. Most patients have a combination of the two. An excellent article on the subject was published in AJR in 2007 (AJR 2007; 188:1540-1552). Please see this for additional detail.