Avascular necrosis of the hip.

Standard radiography versus MRI as a tool for the diagnosis of avascular necrosis. These panels illustrate that standard radiography could be strictly normal at the first clinical sign while MRI is already highly abnormal. The top panel shows the normal appearance of the hip using standard radiography. The middle and bottom panels show 2 different MRI sequences showing that, although the femoral head is still spherical, the adjacent bone is already affected with necrosis, with even cartilage modification.