This is an uncommon condition caused by loss of blood supply to the hip, though it can affect other joints. Nobody knows why it happens, but it especially occurs in persons on long-term steroids, those taking anti-rejection medications for organ transplants, alcoholism, Lupus, Sickle Cell Disease (not Trait), AIDS, and other rare conditions. Hip pain progresses gradually, until the joint is destroyed
Diagnosis is usually easy by x-ray, although in early stages, an MRI may be required. The only treatment is hip replacement surgery once the pain is such that pain medicines are no longer effective.