Avascular necrosis, also known as osteonecrosis, is a disorder in which the bone tissue dies because it does not receive enough blood. Necrosis results in small breaks that can eventually cause the bone to collapse entirely. It most commonly occurs in the hip. Necrosis may occur as a result of a fracture or dislocation, excessive alcohol use, extended use of corticosteroids, or certain diseases such as sickle cell anemia, diabetes, lupus or HIV. Medications taken for osteoporosis or bone cancer, and radiation therapy also increase the risk of a patient developing avascular necrosis.