Osteonecrosis is a disease caused by reduced blood flow to bones in the joints. In people with healthy bones, new bone is always replacing old bone. In osteonecrosis, the lack of blood causes the bone to break down faster than the body can make enough new bone. The bone starts to die and may break down.

You can have osteonecrosis in one or several bones. It is most common in the upper leg. Other common sites are your upper arm and your knees, shoulders and ankles. The disease can affect men and women of any age, but it usually strikes in your thirties, forties or fifties.

At first, you might not have any symptoms. As the disease gets worse, you will probably have joint pain that becomes more severe. You may not be able to bend or move the affected joint very well.

No one is sure what causes the disease. Risk factors include

• Long-term steroid treatment
• Alcohol abuse
• Joint injuries
• Having certain diseases, including arthritis and cancer

Doctors use imaging tests and other tests to diagnose osteonecrosis. Treatments include medicines, using crutches, limiting activities that put weight on the affected joints, electrical stimulation and surgery.

The bones of the human body are made up of living cells that need a blood supply to stay healthy. In osteonecrosis, blood flow to part of a bone is disrupted. This results in death of bone tissue, and the bone can eventually break down and the joint will collapse. Osteonecrosis is also called:

• Avascular necrosis.
• Aseptic necrosis.
• Ischemic necrosis of bone.

Osteonecrosis can happen to any bone, but most often it develops in the ends of long bones, such as the:

• Thigh bone (femur), especially the upper part—the ball in the hip socket. The lower end, which is part of the knee joint, is also often affected.
• Upper arm bone (humerus), especially the upper part—the ball in the shoulder joint.

When the disease involves part of a bone in a joint, it can lead to the breakdown of the bone and arthritis.

Less often, the bones of the elbows, ankles, feet, wrists and hands are affected.

The primary symptom of osteonecrosis is pain, and doctors usually diagnose the disease using imaging methods such as x-rays or magnetic resonance imaging (MRI). Most people require surgical treatment to prevent further bone damage, to protect the bones and joints, and to improve use of the joints.

Osteonecrosis does not always cause symptoms, especially when it first develops. As the disease gets worse, you may feel pain when you put your weight on a joint that is affected by osteonecrosis. Over time, you may feel pain in the joint even when you are resting.

Pain caused by osteonecrosis may be mild or severe. If it causes your bone and joint to collapse, you may have severe pain and not be able to use the joint. For instance, if you have osteonecrosis in the hip, you may not be able to walk.

Osteonecrosis results from the loss of blood supply to the bone. Loss of blood supply to the bone can be caused by:

Medicines or Medical Procedures

• Chemotherapy.
• Radiation therapy.
• High-dose steroids.
• Organ transplants.

Medical Conditions

• Cancer.
• Lupus.
• HIV/AIDS.
• Gaucher’s disease.
• Decompression sickness, also known as divers' disease, the bends, or caisson disease.
• Gout.
• Vasculitis.
• Osteoarthritis.
• Osteoporosis.
• Blood disorders, such as sickle cell disease.

Alcohol Use

Excessive alcohol use causes fatty substances to build up in the blood vessels. This can cause a decreased blood supply to the bone, which can lead to osteonecrosis.

Injury

A broken or dislocated bone, or a joint injury, may damage the surrounding blood vessels. This can cause a decreased blood supply to the bone, which can lead to osteonecrosis.

Anyone can get osteonecrosis, but certain factors increase your risk of developing the disease.

Sex

Generally, osteonecrosis is much more common in males than in females.

Age

Osteonecrosis most commonly occurs in people who are in their 30s, 40s, and 50s.

Medicines or Medical Treatments

Some medicines or medical treatments increase the risk of osteonecrosis:

• Chemotherapy.
• Radiation therapy.
• High-dose steroids.
• Organ transplants.

Medical Conditions

Some medical conditions increase the risk of osteonecrosis:

• Cancer.
• Lupus.
• HIV/AIDS.
• Gaucher’s disease.
• Decompression sickness, also known as divers' disease, the bends, or caisson disease.
• Gout.
• Vasculitis.
• Osteoarthritis.
• Osteoporosis.
• Blood disorders, such as sickle cell disease.

Alcohol Use

Excessive alcohol use causes fatty substances to build up in the blood vessels. This can cause a decreased blood supply to the bone, which can lead to osteonecrosis.

Injury

A broken or dislocated bone or a joint injury may damage the surrounding blood vessels. This can cause a decreased blood supply to the bone, which can lead to osteonecrosis.

If your doctor suspects you have osteonecrosis, he or she will take your medical history and do a physical exam. Your doctor may also order one or more tests to see which bones are affected and the amount of bone affected.

X-Ray

An x-ray is a picture of the bones that may help your doctor diagnose the cause of your pain. However, an x-ray is not sensitive enough to detect bone changes that may be a sign of osteonecrosis; because of this, your doctor may order more tests even if your x-ray is normal. As osteonecrosis worsens, an x-ray may show bone damage caused by the disease. If you are diagnosed with osteonecrosis, x-rays are often used to monitor the disease.

Magnetic Resonance Imaging (MRI)

An MRI is a form of imaging that detects chemical changes in the bone marrow. It provides your doctor with a picture of the part of your bone or bones that are affected by osteonecrosis, whether or not you have symptoms, and how well your bones are rebuilding themselves. An MRI is the most sensitive test for diagnosing osteonecrosis in its earliest stages.

Computed Tomography (CT) Scan

A CT scan is a form of imaging that provides your doctor with a 3D (three-dimensional) picture of your bones. A CT scan also shows “slices” of the bone, making the picture much clearer than an x-ray or bone scan. However, not all doctors agree that CT scans are useful to diagnose osteogenesis. Although doctors can usually diagnosis osteonecrosis without a CT scan, it may be useful in determining the extent of bone damage.

Bone Scan

A bone scan is a form of imaging that is used in patients who have normal x-rays and no risk factors for osteonecrosis. A bone scan can detect all bones and joints in the body that are affected by osteonecrosis. In this test, a harmless radioactive material is injected into the body, and then a picture of the bone is taken with a special camera. The picture shows how the injected material travels through blood vessels in bone.

Biopsy

A biopsy is a surgical procedure in which a tissue sample from your bone is removed and studied to determine whether you have osteonecrosis. A biopsy is rarely recommended because it requires surgery.

Functional Evaluation of Bone

If you have normal x-rays, MRIs, and bone scans buy your doctor still suspects you may have osteonecrosis, he or she may order tests that measure the pressure inside of your bone or bones. Increased pressure is a sign that you may have osteonecrosis.

Osteonecrosis that is diagnosed early is easier to effectively treat.

There are several treatments for osteonecrosis. The goals of treatments are to:

• Improve use of the joint.
• Stop further damage.
• Protect bones and joints.

Your treatment options may include surgery or nonsurgical treatments, such as medicines. Your doctor will determine the best treatment for you based on several factors, including:

• Your age.
• The stage of the disease.
• Where and how much bone has osteonecrosis.
• The cause, if known. If the cause is steroid or alcohol use, treatment may not work unless you stop using those substances.

Nonsurgical Treatments

Non-surgical treatments do not cure osteonecrosis, but they may help manage the disease. Your doctor may recommend one or more non-surgical treatments, especially if the disease is in its early stages:

Medications

• Nonsteroidal anti-inflammatory drugs (NSAIDs) are used to reduce pain and swelling.
• If you have blood-clotting problems, blood thinners may be used to prevent clots that block the blood supply to the bone.
• If you take steroid medicines, cholesterol-lowering drugs may be used to reduce fat in the blood.

Taking Weight Off the Joint

Your doctor may suggest you limit your activity or use crutches to take weight off joints with osteonecrosis. This may slow bone damage and allow some healing. If combined with NSAIDs, it may help you avoid or delay surgery.

Range-of-Motion Exercises

Your doctor may recommend you exercise the joints with osteonecrosis to help improve their range of motion.

Electrical Stimulation

Your doctor may recommend electrical stimulation therapy to help bone growth.

Surgery

Most people with osteonecrosis eventually need surgery as the disease worsens. Some people with early stage disease may need surgery if non-surgical treatments do not help.

There are four types of surgery. Your doctor will decide if you need surgery and what type is best for you.

• Core decompression surgery, which lowers the pressure inside the bone. This increases blood flow to the bone.
• Osteotomy, which reshapes the bone. This reduces stress on the damaged joint.
• Bone graft, which takes healthy bone from one part of the body and uses it to replace diseased bone.
• Total joint replacement, which replaces the joint with a man-made one.