What Is Avascular Necrosis of the Hip, and How Is It Detected?

Your hip joint is a ball and socket. The ball, the femoral head, sits at the top of the thigh bone and fits snugly into the pelvis. It needs a steady blood supply to stay healthy. When that supply is interrupted, bone starts to break down from the inside. This is avascular necrosis.

AVN can progress quietly. Many people feel only a dull ache at first, sometimes mistaken for a muscle strain. Without the right imaging at the right time, the condition may not be recognised until the bone surface has already started to crumble.

What does avascular necrosis of the hip feel like?

In its earliest stages, AVN may cause no pain at all. As the bone weakens, you typically notice a deep, aching discomfort in the groin or front of the hip. Pain often worsens with weight-bearing and eases when you rest.

If you develop sudden, severe hip pain, loss of ability to bear weight, or any numbness or weakness in the leg, seek urgent medical attention through your GP, 111 or A&E rather than booking a scan.

What causes avascular necrosis of the hip?

Anything that reduces or blocks blood flow to the femoral head can trigger AVN. Sometimes a clear cause is found. In other cases, no single factor is identified.

Other less common triggers include radiation therapy, autoimmune conditions and diving-related decompression illness. When no cause is found, the condition is called idiopathic AVN.

How is avascular necrosis of the hip detected?

MRI is the gold-standard tool for early detection. It can reveal changes in the bone marrow and blood supply before any damage shows up on a standard X-ray. If your doctor suspects AVN, an MRI should usually be the first step.

Standard X-rays may appear completely normal in the early stages. By the time X-ray shows a clear problem, the femoral head may already be flattening or collapsing. That is why early MRI matters so much.

Why does standing alignment matter when you have AVN?

Standing alignment matters because the damage AVN causes changes the way your body carries its weight. A weakening femoral head shifts your load onto the opposite leg, tilts your pelvis and can alter the curves of your spine. These compensations often cause pain in places far from the hip itself.

Lying-down scans relax the muscles and take gravity out of the equation. They can hide the pelvic tilt, the leg-length difference and the spinal shift that appear only when you are upright. A standing whole-body image captures all of this in a single exposure, from your ankles to your spine, under real weight-bearing conditions.

This is what ScanAlign standing EOS imaging provides. A full-length, weight-bearing image that shows how AVN in one hip is affecting the rest of your skeleton. Your consultant can then plan treatment based on the complete mechanical picture, not just the damaged bone in isolation.

What are the general options if AVN is found?

Treatment depends on how far the condition has progressed and how much of the femoral head is affected. ScanAlign is a diagnostic imaging clinic, so we do not provide treatment ourselves. But understanding the general options helps you ask the right questions when you see your specialist.

In early stages, when the bone surface is still intact, joint-preserving procedures such as core decompression may be considered. The aim is to relieve pressure inside the bone and encourage new blood vessels to form. Other approaches include bone grafting or medications to slow bone loss.

When the femoral head has already begun to collapse or flatten, a hip replacement may become the most reliable option. Standing alignment imaging is particularly useful at this point. It helps the surgical team plan the replacement around your actual weight-bearing mechanics, including any pelvic tilt or leg-length difference that has developed.

If you are experiencing hip pain and alignment problems alongside a known AVN diagnosis, understanding both the bone damage and the mechanical consequences gives your specialist the fullest possible picture.

Frequently asked questions about avascular necrosis of the hip