What happens to people who get avascular necrosis of the hip (also called osteonecrosis)?

Usually surgery: If the problem gets very severe you will start to have some collapse in the femoral head and you may ultimately require a total hip arthroplasty.

Depends on severity: Avascular necrosis is also known as avn or osteonecrosis- a condition in which the blood supply to the hip ball (the femoral head) is compromised. There are different staging systems for avn- designed to identify the severity of the disease, and thereby help with treatment recommendations. Treatment ranges from observation to a "core decompression" procedure to hip replacement.