What Is Avascular Necrosis? Key Information

Avascular necrosis is a condition where bone tissue dies because its blood supply has been cut off. The word “avascular” means without blood, and “necrosis” means tissue death. It most often affects the hip, but it can also occur in the shoulder, knee, ankle, and jaw. Without treatment, the affected bone can collapse and lead to severe arthritis.

What Is Avascular Necrosis and How Does It Happen?

Bone is living tissue. Like every other part of the body, it needs a steady flow of blood to survive and repair itself. When that blood flow is interrupted — whether by injury, disease, or medication — bone cells begin to die. This process is called avascular necrosis.

The condition usually develops in the ends of long bones, near joints. The femoral head — the ball at the top of the thigh bone that fits into the hip socket — is the most common site. That’s because this area has a relatively fragile blood supply compared to other bones.

Once blood flow stops, the bone doesn’t collapse immediately. The dead bone retains its shape for a while. But the body can’t repair it without circulation. Over time, small fractures develop in the dead bone, and the surface may flatten or break apart. When that happens, the joint stops working smoothly. Pain increases, and arthritis follows.

This is why early detection matters. Before the bone collapses, there may be a window where treatment can slow or stop the process. After collapse, the options narrow considerably.

What Causes Avascular Necrosis?

The causes fall into two broad groups: traumatic and non-traumatic. In traumatic cases, a physical injury damages the blood vessels feeding the bone. A hip fracture or dislocation is a common example. The force of the injury tears or compresses the vessels, and blood flow is lost.

Non-traumatic causes are more varied and sometimes less clear. The strongest known risk factor is long-term, high-dose corticosteroid use. These are powerful anti-inflammatory medications used for conditions like lupus, rheumatoid arthritis, and organ transplant rejection. Research has consistently linked steroids to avascular necrosis, though the exact mechanism is not fully understood. It may involve changes in fat metabolism that block small blood vessels.

Excessive alcohol consumption is another well-established risk factor. The relationship is dose-dependent — heavier and longer use raises risk. Again, the mechanism is not entirely clear, but altered fat metabolism and increased pressure inside the bone are thought to play roles.

Other conditions associated with avascular necrosis include:

• Sickle cell disease, which can cause blood vessel blockage
• Gaucher disease, a rare genetic disorder
• Radiation therapy
• Decompression sickness (the bends) in divers
• Certain blood clotting disorders

In many cases, no cause is identified. These are called idiopathic cases. Some research suggests that genetic factors may make certain people more vulnerable, but this is still an area of active study.

What Are the Symptoms of Avascular Necrosis?

Early avascular necrosis often causes no symptoms at all. The bone may be dying, but pain doesn’t always follow right away. This silent phase can last for months or longer.

When symptoms do appear, pain is usually the first sign. It’s often felt in the groin, buttock, or thigh for hip involvement. Initially, the pain may only occur with activity. As the condition progresses, it can become constant — even at rest. Night pain is common in later stages.

Other symptoms include:

• Limited range of motion in the affected joint
• Stiffness, especially after sitting or resting
• A limp, if the hip is involved
• Pain that worsens over time

The pattern varies depending on which bone is affected. In the knee, pain may be felt on the inside of the joint. In the shoulder, it may be felt at the top of the arm. In the jaw, it can cause pain with chewing.

Because early symptoms are vague, avascular necrosis is sometimes mistaken for a muscle strain or arthritis. That delay can be costly. If you have persistent joint pain and any known risk factors, it’s worth mentioning to a doctor.

How Is Avascular Necrosis Diagnosed?

Diagnosis starts with a medical history and physical exam. A doctor will ask about pain patterns, risk factors, and any previous injuries. They’ll also check range of motion and look for signs of joint damage.

Imaging is essential. X-rays can show changes in bone shape and density, but they often appear normal in early stages. That’s because X-rays primarily show bone structure, not blood flow.

MRI is the most sensitive imaging test for avascular necrosis. It can detect the condition before X-ray changes appear. MRI can also show how much bone is affected and whether the joint surface has started to collapse. This information guides treatment decisions.

In some cases, a bone scan may be used. This involves injecting a small amount of radioactive material that collects in areas of abnormal bone turnover. It’s less specific than MRI but can be useful when MRI isn’t available or isn’t an option.

Staging systems help classify the severity. The most commonly used system divides the condition into stages based on imaging findings — from early changes with normal X-rays to late-stage collapse with joint destruction. Staging helps determine which treatments are appropriate.

What Treatment Options Exist for Avascular Necrosis?

Treatment depends on several factors: the stage of the disease, the size and location of the affected area, the person’s age, and their overall health. The goal is to preserve the joint if possible, or replace it if necessary.

Non-surgical approaches may be tried in early stages. These include:

• Activity modification to reduce stress on the affected joint
• Pain medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs)
• Physical therapy to maintain strength and range of motion

These measures can help manage symptoms, but they don’t reverse the underlying process. They may slow progression in some cases, but the evidence for this is limited.

Surgical options are often needed, especially when the condition is advanced or progressing. These include:

• Core decompression: A procedure that removes a small cylinder of bone from the affected area. This may reduce pressure inside the bone and encourage new blood vessel growth. It’s most effective in early stages before collapse.
• Bone grafting: Healthy bone is transplanted into the dead area to provide structural support and possibly new blood supply.
• Osteotomy: The bone is cut and repositioned to shift weight away from the damaged area. This is less common now than in the past.
• Total joint replacement: When the joint is severely damaged, replacing it with an artificial joint can relieve pain and restore function. This is often the most reliable option for late-stage disease.

Newer approaches are being studied. These include stem cell therapy and various medications aimed at improving blood flow or slowing bone death. Some early research is promising, but no large human trials have confirmed that these approaches are broadly effective. They remain experimental.

Can Avascular Necrosis Be Prevented?

There is no sure way to prevent avascular necrosis, especially when it results from trauma. But some steps may lower risk in certain situations.

If you take corticosteroids, talk to your doctor about the lowest effective dose and whether alternatives exist. Never stop a prescribed medication without medical guidance. The risks of abruptly stopping steroids can be serious.

Limiting alcohol intake is also reasonable. Heavy, long-term alcohol use is a known risk factor. Reducing consumption may lower risk, though the exact threshold at which risk increases is not clearly defined.

For people with sickle cell disease or other conditions that affect blood flow, regular medical care and monitoring can help catch problems early. Early detection may allow for treatments that preserve the joint.

If you have a joint injury — especially a hip fracture or dislocation — follow your doctor’s advice for follow-up. Some research suggests that early stabilization of certain fractures may reduce the risk of avascular necrosis, but this is not universally established.

What Is the Outlook for Someone With Avascular Necrosis?

The outlook varies widely. In early stages, before the bone collapses, treatment may delay or prevent further damage. Some people stabilize and do well for years. Others progress despite treatment.

Once the bone collapses, the joint usually deteriorates. Pain and disability increase. At that point, joint replacement is often the most effective option. Hip replacement, in particular, is a well-established procedure with good long-term outcomes for most people.

The underlying cause matters. Cases linked to steroids or alcohol may progress differently than those from trauma. Age and overall health also play roles. Younger people tend to have more aggressive disease, possibly because they have higher bone turnover.

Regular follow-up is important. Imaging may be repeated to monitor progression. If symptoms worsen, treatment plans may need to change.