Describe the features of avascular necrosis.?

Avascular necrosis: Bone death caused by poor blood supply to the area due to disease or severe trauma. It is most common in the hip and shoulder, but can affect other large joints such as knee, elbow, wrist and ankle. If untreated, the bone can eventually collapse and cause further problems. (see also: http://www.Ncbi.Nlm.Nih.Gov/pubmedhealth/pmh0004519/ ).