Avascular Necrosis: Causes, Symptoms, and Diagnosis

Most people think of hip disease as something that comes with age. Avascular necrosis (AVN), also called osteonecrosis, often strikes decades earlier—in a person’s 20s, 30s, or 40s. It happens when the blood supply to a bone is disrupted, and the bone tissue begins to die, most often in the femoral head—the ball portion of the hip joint.

Left untreated, the affected bone can collapse under ordinary mechanical stress, leading to severe osteoarthritis and, eventually, a need for total hip replacement.

Because people with AVN tend to be younger than typical hip-replacement patients, this can also mean a lifetime risk of prosthetic wear and future revision surgery, which is a repeat operation to replace a worn or failing implant.

But Yale Medicine’s Daniel Wiznia, MD, an associate professor of orthopaedics and rehabilitation at Yale School of Medicine and co-director of the Yale Avascular Necrosis and Osteonecrosis Program, is pioneering sophisticated, joint-preserving interventions. Dr. Wiznia’s innovative work focuses on intercepting the disease early using advanced 3D navigated technology and new surgical techniques.

Dr. Wiznia answers common questions about the condition, how it’s diagnosed, and ways to help preserve the joint.

AVN is a condition where bone tissue dies because its blood supply has been disrupted or reduced. It most often affects the femoral head—a form of the condition referred to as osteonecrosis of the femoral head.

Without a healthy blood supply, the bone loses structural integrity, and the femoral head can eventually collapse. This collapse destroys the smooth mechanics of the hip joint and can lead to severe hip osteoarthritis and painful joint degeneration.

AVN differs from the joint diseases that typically affect older adults, and it can affect mobility for decades if it isn’t caught and treated early. Early detection is critical.

Osteonecrosis develops when blood flow to a bone is reduced or interrupted, causing the bone cells to die. Common risk factors include corticosteroid exposure, alcohol use disorder, trauma or dislocation, sickle cell disease and other blood disorders, autoimmune disease, chemotherapy protocols, radiation, clotting disorders, kidney disease or transplant history, metabolic disease, and certain genetic or systemic conditions.

Some people develop AVN after a major illness or medical treatment, while others have no single identifiable cause. Because AVN can affect multiple joints, evaluation shouldn’t stop at the hip.

AVN can be very painful, but early-stage disease may also be painless or produce only vague signs. When symptoms do appear, people typically describe pain in the groin, deep hip, or buttock, or pain that radiates toward the thigh or knee.

Pain is usually worse with weight-bearing activity and may improve with rest, though it can become more constant as the femoral head weakens or collapses. Because these symptoms overlap with muscle strain, arthritis, a labral tear, a stress fracture, or other causes of hip pain, AVN is frequently missed or diagnosed late.

AVN isn’t inherited through a single gene, but genetics and certain inherited conditions can raise a person’s risk—for example, sickle cell disease, thrombophilia, Gaucher disease, Fabry disease, COL2A1-related disorders, and familial forms of osteonecrosis.

A family history of AVN is a reason for closer evaluation. In most people, though, AVN results from an interaction between genetic predisposition, vascular health, medication exposure, alcohol use, trauma, metabolic disease, and inflammatory or blood disorders.

Ideally, AVN is diagnosed before the femoral head collapses, but it’s often found after symptoms develop. Standard X-rays can look normal in early-stage AVN, so clinically significant disease can be present even when X-rays appear reassuring.

That’s why we use MRI to define the size, location, and extent of the necrotic, or dead, lesion. It’s the most effective test for early detection. Because AVN can occur in both hips at once, both should be evaluated.

Progression varies widely, depending on the lesion’s size, location, and stage. The underlying cause and whether the femoral head has already begun to collapse are important factors, too.

Some small, early lesions may remain stable for a long time, while larger or later-stage lesions can progress to collapse in months to a few years.

Hyperbaric oxygen combined with core decompression surgery can preserve the joint in hips that have not yet collapsed. At Yale’s Avascular Necrosis and Osteonecrosis Program, we emphasize early MRI diagnosis, careful staging, and rapid treatment by our multidisciplinary hip-preservation team before that window closes.

Once the femoral head begins to collapse, the joint surface loses its round shape and cartilage damage leads to osteoarthritis. This substantially raises the likelihood that a total hip replacement will eventually be needed.

AVN doesn’t spread the way an infection does. But if the underlying risk factor isn’t well managed, AVN can spread from one bone to another, and existing lesions can grow in size. The same risk factors that caused AVN in one hip can also affect the opposite hip and other joints.

It’s common for people with systemic risk factors to have AVN in both hips at the same time. That’s why anyone diagnosed with AVN in one hip should have the other hip evaluated. Pain in other joints known to be at risk for AVN—such as the knees, shoulders, elbows, ankles, or wrists—should also be evaluated.

AVN is not usually a life-threatening diagnosis, and people with it can expect a normal lifespan. The main concerns are about pain, loss of mobility, femoral head collapse, arthritis, and the potential need for hip replacement at a young age—not survival.

People with AVN often have underlying medical conditions that need to be identified so the risk factors driving the disease can be managed.

In early-stage AVN, joint-preserving treatment may reduce pain, delay collapse, and postpone or even prevent the need for total hip replacement. In advanced stages, hip replacement reliably relieves pain and restores function.

Because AVN often affects younger people, they may face a longer lifetime risk of needing revision surgery than older patients who have had a hip replacement for other reasons.

No, AVN can’t return in the femoral head itself, since that portion of bone is removed during hip replacement. But the underlying condition that caused AVN can still be present, which means the opposite hip or other joints may remain at risk. People who have other risk factors may need continued monitoring even after one hip has been replaced.

Our program stands out by treating the whole patient. Rather than evaluating only the affected joint, our multidisciplinary team—which may include hematologists, rheumatologists, radiologists, and hyperbaric oxygen medicine experts—collaborates to identify underlying risk factors and the root cause of AVN.

Their shared objective is to provide rapid diagnosis through MRI and use targeted interventions before the window for joint preservation closes—they’re really focused on preserving the patient’s hip whenever possible.

Our team also coordinates care for any conditions that may have contributed to AVN, screens for other potential sites affected by AVN, develops treatment protocols, and matches treatment options to each patient’s unique disease stage and risk profile.

If you’re having hip, groin, or buttock pain that doesn’t ease with rest—or if you have a known risk factor for AVN, such as long-term steroid use, sickle cell disease, or a family history of the condition—it’s worth asking your doctor whether an MRI is appropriate.