Avascular Necrosis (AVN or Osteonecrosis)

Medically Reviewed by Dan Brennan, MD on October 25, 2022
Written by Mary Anne Dunkin
5 min read

Avascular necrosis (AVN) is the death of bone tissue due to a loss of blood supply.  You might also hear it called osteonecrosis, aseptic necrosis, or ischemic bone necrosis.

If it isn’t treated, AVN can cause the bone to collapse. AVN most often affects your hip. Other possible sites are the shoulder, knees, and ankles.

In its earliest stages, AVN may have no symptoms, but as the disease progresses it typically becomes very painful. At first, it might only hurt when you put pressure on the affected bone. Then, pain may become constant. If the bone and surrounding joint collapse, you may have severe pain that makes you unable to use your joint. The time between the first symptoms and bone collapse can range from several months to more than a year.

Things that can make avascular necrosis more likely include:

  • Alcohol. Several drinks a day can cause fat deposits to form in your blood, which lower the blood supply to your bones.
  • Bisphosphonates. These medications that boost bone density could lead to osteonecrosis of the jaw. This could be more likely if you’re taking them for multiple myeloma or metastatic breast cancer.
  • Medical treatments. Radiation therapy for cancer can weaken bones. Other conditions linked to AVN include organ transplants, like kidney transplants.
  • Steroid drugs. Long-term use of these inflammation-fighting drugs, either by mouth or in a vein, leads to 35% of all cases of nontraumatic AVN. Doctors don’t know why, but longtime use of medications like prednisone can lead to AVN. They think the meds can raise fat levels in your blood, which lowers blood flow.
  • Trauma. Breaking or dislocating a hip can damage nearby blood vessels and cut the blood supply to your bones. AVN may affect 20% or more of people who dislocate a hip.
  • Blood clots, inflammation, and damage to your arteries. All of these can block blood flow to your bones.

Other conditions associated with nontraumatic AVN include:

As many as 20,000 people develop AVN each year. Most are between ages 20 and 50. For healthy people, the risk of AVN is small. Most cases are the result of an underlying health problem or injury.

Your doctor will start with a physical exam. They’ll press on your joints to check for tender spots. They’ll move your joints through a series of positions to check your range of motion. You might get one of these imaging tests to look for what’s causing your pain:

  • Bone scan. The doctor injects radioactive material into your vein. It travels to spots where bones are injured or healing and shows up on the image.
  • MRI and CT scan. These give your doctor detailed images showing early changes in bone that might be a sign of AVN.
  • X-rays. They’ll be normal for early stages of AVN but can show bone changes that appear later on.

Treatment goals for AVN are to improve the joint, stop the bone damage, and ease pain. The best treatment will depend on a number of things, like:

  • Your age
  • Stage of the disease
  • Location and amount of bone damage
  • Cause of AVN

If you catch avascular necrosis early, treatment may involve taking medications to relieve pain or limiting the use of the affected area. If your hip, knee, or ankle is affected, you may need crutches to take weight off the damaged joint. Your doctor may also recommend range-of-motion exercises to help keep the joint mobile.

  • Medications. If the doctor knows what’s causing your avascular necrosis, treatment will include efforts to manage it. This can include:
    • Blood thinners. You’ll get these if your AVN is caused by blood clots.
    • Nonsteroidal anti-inflammatory drugs (NSAIDs). These will help with pain.
    • Cholesterol drugs. They cut the amount of cholesterol and fat in your blood, which can help prevent the blockages that lead to AVN.
  • Surgery. While these nonsurgical treatments may slow down the avascular necrosis, most people with the condition eventually need surgery. Surgical options include:
    • Bone grafts. Removing healthy bone from one part of the body and using it to replace the damaged bone
    • Osteotomy. Cutting the bone and changing its alignment to relieve stress on the bone or joint
    • Total joint replacement. Removing the damaged joint and replacing it with a synthetic joint
    • Core decompression. Removing part of the inside of the bone to relieve pressure and allow new blood vessels to form
    • Vascularized bone graft. Using your own tissue to rebuild diseased or damaged hip joints. The surgeon first removes the bone with the poor blood supply from the hip, then replaces it with the blood-vessel-rich bone from another site, such as the fibula, the smaller bone in your lower leg.
    • Electrical stimulation. An electrical current could jump-start new bone growth. Your doctor might use it during surgery or give you a special gadget for it.

You can do these things to help:

  • Rest. Stay off the joint. This can help slow damage. You might need to hold back on physical activity or use crutches for several months.
  • Exercise. A physical therapist can show you the right moves to get range of motion back in your joint.

To lower your risk of AVN:

  • Cut back on alcohol. Heavy drinking is a leading risk factor for AVN.
  • Keep your cholesterol in check. Small bits of fat are the most common thing blocking blood supply to you bones.
  • Use steroids carefully. Your doctor should keep tabs on you while you’re taking these medications. Let them know if you’ve used them in the past. Taking them over and over again can worsen bone damage.
  • Don't smoke. It boosts your AVN risk.

More than half the people with this condition need surgery within 3 years of diagnosis. If a bone collapse in one of your joints, you’re more likely to have it happen in another.

Your outlook depends on several things:

  • Disease stage at the time you were diagnosed
  • If you have an underlying condition

You’re less likely to do well if:

  • You’re over 50.
  • You’re at stage III or higher when you’re diagnosed.
  • More than a third of the bone’s weight-bearing area is dead.
  • The damage goes past the end of the bone.
  • You have a long history of cortisone treatments.