X-ray of the pelvis of a 24 year old female patient with osteochondritis dissecans (OCD) and dysplasia of both hips. OCD affects the head of the femur (thighbone), where it articulates with the hip. It occurs when a small fragment of cartilage and bone separates from the joint. The fragment may stay in place or fall into the joint, where it causes swelling and pain, and may cause the joint to lock. Here it is also causing dysplasia, a condition where the hip socket is too shallow to fully accommodate the femur head.