Avascular necrosis, otherwise known as osteonecrosis or aseptic necrosis is a painful condition that occurs when the blood supply to the bone is disrupted. Avascular necrosis can ultimately lead to destruction of the joint and severe arthritis. Although the process can occur in any bone, osteonecrosis most often affects the hip. More than 20,000 people each year enter hospitals for treatment of osteonecrosis of the hip. In many cases, both hips are affected by the disease.