| Note the wedge-shaped area of avascular necrosis (osteonecrosis) at the upper right of this femoral head. Avascular necrosis results from bone ischemia, which can be due to many causes, including trauma and corticosteroid administration, though idiopathic cases are common. There is pain with activity, progressing to pain at rest. Eventually, the necrotic bone collapses, distorting the overlying articular cartilage and producing secondary osteoarthritis. [Image courtesy of John Nicholls MD, Hong Kong University] |
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