In 2014, I was diagnosed with avascular necrosis of the hips. That's when my nightmare began. What is avascular necrosis? Avascular necrosis (AVN), also known as osteonecrosis of the femoral head, occurs when the blood supply to the bone is decreased. This interruption in blood supply causes small cracks and breaks in the bone. If the AVN is left untreated, the bone will eventually die and collapse. Over 20,000 people acquire AVN every year, typically between 20 and 50 years old. It can be caused by a number of factors, such as damage to the bone's blood supply, or injury to the bone itself, which can damage blood vessels and precipitate AVN.