The joint space is maintained in the hip. The subchondral bone of the femoral head has lost its sharp definition, and there is haziness of the underlying trabeculae. The radiolucent crescent line is a plane of cleavage or fracture and is best seen in the abduction position early in the disease. Significant sclerosis is not yet evident. The femoral head is not flattened but may become so later in the disease process.