Avascular necrosis (also called osteonecrosis, aseptic necrosis, or ischemic bone necrosis) is a disease that results from the temporary or permanent loss of blood supply to the bone. When blood supply is cut off, the bone tissue dies and the bone collapses. If avascular necrosis occurs near a joint, collapse of the joint surface may occur.
Avascular necrosis may occur in any bone, but most commonly occurs in the ends of a long bone. It may affect one bone, several bones at one time, or different bones at different times.