Avascular necrosis (AVN), which is also known as osteonecrosis, aseptic necrosis, and ischemic bone necrosis, is a condition which occurs when there is a loss of blood to the bone. Bone is living tissue, and therefore requires blood to survive. When there is an interruption to the blood supply, the bone begins to die. If not stopped, the lack of blood will eventually cause the bone to collapse.
Avascular necrosis typically occurs in the upper leg. Other common areas are the upper arm, knees, shoulder, and ankles.