The causes of avascular necrosis are not completely understood, but it appears to be related to an interruption in blood flow to the femoral ball. Here are some possible reasons:
1. Damage to the blood vessels due to fracture (e.g. broken hip)
2. Damage to the inside of the blood vessels (e.g. vasculitis, radiation therapy)
3. A clot that clogs the blood vessel (e.g. sickle cell diseases, corticosteroids, alcohol)
Although the cause in bone death is clear in some cases (such as a disruption in blood flow from a break in the bone or a clot in the blood vessels) the cause in most cases is poorly understood. People who have used large amounts of steroids or alcohol for long periods of time may have a higher risk of developing this disease.