Illustration of a femoroacetabular impingement, between the femoral neck and the acetabular cavity (or cup). The impingement originated with the presence of a bump of the upper front part of the femoral neck, and/or a cup that overly covers the top and exterior of the femur. These anatomical anomalies can cause, with repeated contact in these areas, lesions on the acetabular bulge and the joint cartilage which can lead to premature osteoarthritis in the hip.