Definition of Osteonecrosis:

Osteonecrosis is bone death caused by poor blood supply to the area. It is most common in the hip and shoulder, but can affect other large joints such as knee, elbow, wrist and ankle.

Causes, incidence, and risk factors:

Osteonecrosis occurs when part of the bone does not get blood and dies. After a while the bone can collapse. If this condition is not treated, the joint will deteriorate and this will become severe arthritis.

Osteonecrosis can be caused by disease, or a severe trauma, such as a break or dislocation, that affects the blood supply to the bone. Many times, no trauma or disease is present. This is called "idiopathic osteonecrosis" -- meaning it occurs without any known cause.

The following can cause osteonecrosis:

• Long-term treatments with steroids
• Excessive alcohol use
• Sickle cell disease
• Radiation therapy
• Gaucher disease
• Decompression sickness from a lot of deep sea diving
• Dislocation or fractures around a joint

Some diseases that may be associated with the development of this condition include:

• Gout
• Atherosclerosis
• Diabetes

When osteonecrosis occurs in the shoulder joint, it is usually due to long-term treatment with steroids or a history of trauma to the shoulder.

Legg-Calvé-Perthes disease is a similar condition seen in children and adolescents.