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Guide to Avascular Necrosis


Updated June 27, 2014

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Part 1 of 8 - What Is Avascular Necrosis?

What Is AVN?

Avascular necrosis (AVN) is a disease resulting from the temporary or permanent loss of the blood supply to the bones. Without blood, the bone tissue dies and causes the bone to collapse. If the process involves the bones near a joint, it often leads to collapse of the joint surface. It also is known as:

  • osteonecrosis
  • aseptic necrosis
  • ischemic bone necrosis

Bones Affected

Although it can happen in any bone, AVN most commonly affects the ends (epiphysis) of long bones such as the femur (bone that extends from the knee joint to the hip joint) Other common sites include the:

The disease may affect just one bone, more than one bone at the same time, or more than one bone at different times.


The amount of disability that results from AVN depends on:

  • what part of the bone is affected
  • how large an area is involved
  • how effectively the bone rebuilds itself

The process of bone rebuilding takes place after an injury as well as during normal growth. Normally, bone continuously breaks down and rebuilds, old bone is reabsorbed and replaced with new bone. The process keeps the skeleton strong and helps it to maintain a balance of minerals. In the course of AVN, however, the healing process is usually ineffective and the bone tissues break down faster than the body can repair them.


If left untreated, the disease progresses, the bone collapses, and the joint surface breaks down, leading to joint pain and osteoarthritis.

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