Figure 1.
An 83-year-old woman developed osteonecrosis and secondary osteoarthritis in the medial femur condyle. The initial radiographs at diagnosis (A) and those after 1 year (B) showed a small but typical radiolucent subchondral lesion in the weight-bearing area of the medial femoral condyle. The patient had a total knee arthroplasty 2 years after diagnosis (C).