Avascular necrosis (osteonecrosis)

Avascular necrosis is the death of bone tissue due to a lack of blood supply. Also called osteonecrosis, it can lead to tiny breaks in the bone and cause the bone to collapse. The process usually takes months to years.

A broken bone or dislocated joint can stop the blood flow to a section of bone. Avascular necrosis is also associated with long-term use of high-dose steroid medications and too much alcohol.

Anyone can be affected. But the condition is most common in people between the ages of 30 and 50.

Some people have no symptoms in the early stages of avascular necrosis. As the condition worsens, affected joints might hurt only when putting weight on them. Eventually, you might feel the pain even when you're lying down.

Pain can be mild or severe. It usually develops gradually. Pain associated with avascular necrosis of the hip might center on the groin, thigh or buttock. Besides the hip, the shoulder, knee, hand and foot can be affected.

Some people develop avascular necrosis on both sides, such as in both hips or in both knees.

See your health care provider for ongoing pain in any joint. Seek immediate medical attention for a possible broken bone or dislocated joint.

Avascular necrosis occurs when blood flow to a bone is interrupted or reduced. Reduced blood supply can be caused by:

• Joint or bone trauma. An injury, such as a dislocated joint, might damage nearby blood vessels. Cancer treatments involving radiation also can weaken bone and harm blood vessels.
• Fatty deposits in blood vessels. The fat (lipids) can block small blood vessels. This can reduce blood flow to bones.
• Certain diseases. Medical conditions, such as sickle cell anemia and Gaucher's disease, also can lessen blood flow to bone.

Sometimes the cause of avascular necrosis not brought on by trauma isn't fully understood. Genetics combined with overuse of alcohol, certain medications and other diseases likely play a role.

Risk factors for developing avascular necrosis include:

• Trauma. Injuries, such as hip dislocation or fracture, can damage nearby blood vessels and reduce blood flow to bones.
• Steroid use. Use of high-dose corticosteroids, such as prednisone, is a common cause of avascular necrosis. The reason is unknown, but some experts believe that corticosteroids can increase lipid levels in the blood, reducing blood flow.
• Drinking too much alcohol. Having several alcoholic drinks a day for several years also can cause fatty deposits to form in blood vessels.
• Bisphosphonate use. Long-term use of medications to increase bone density might contribute to developing osteonecrosis of the jaw. This rare complication has occurred in some people treated with high doses of these medications for cancers, such as multiple myeloma and metastatic breast cancer.
• Certain medical treatments. Radiation therapy for cancer can weaken bone. Organ transplants, especially kidney transplants, also are associated with avascular necrosis.

Medical conditions associated with avascular necrosis include:

• Pancreatitis
• Gaucher's disease
• HIV/AIDS
• Systemic lupus erythematosus
• Sickle cell anemia
• Decompression sickness, also known as divers' disease or the bends
• Certain types of cancer, such as leukemia

Untreated, avascular necrosis worsens. Eventually, the bone can collapse. Avascular necrosis also causes bone to lose its smooth shape, possibly leading to severe arthritis.

To reduce the risk of avascular necrosis and improve general health:

• Limit alcohol. Heavy drinking is one of the top risk factors for developing avascular necrosis.
• Keep cholesterol levels low. Tiny bits of fat are the most common substance blocking blood supply to bones.
• Monitor steroid use. Make sure your health care provider knows about your past or present use of high-dose steroids. Steroid-related bone damage appears to worsen with repeated courses of high-dose steroids.
• Don't smoke. Smoking narrows blood vessels, which can reduce blood flow.