Avascular necrosis occurs when the blood supply to tissue, such as cartilage and bone, is decreased or stopped. Without an adequate blood supply, the tissue breaks down and dies.

Avascular necrosis may be caused by an injury, such as forceful impact in a car crash, or may occur as a complication of a hip fracture or dislocation. Conditions such as sickle cell anemia, gout, and lupus may lead to avascular necrosis. Long-term use of alcohol or medicines, such as corticosteroids, increases the risk of avascular necrosis.