Osteonecrosis of the hip — also called avascular necrosis, or AVN — occurs when the blood supply to the head of the femur (the ball of the ball-and-socket joint) is interrupted. Starved of nutrients and oxygen, the bone dies. So what causes hip osteonecrosis, and what can we do about it?
What causes osteonecrosis of the hip?
We think disruption of the blood supply to the femoral head leads to bone swelling, then bone death and collapse.
Most cases of hip AVN have no identifiable cause. But several risk factors are recognised: cortisone (steroid) use, alcohol intake, trauma such as a hip fracture, inflammatory arthritis such as lupus, sickle cell disease, Crohn’s disease, vasculitis, high cholesterol, and HIV infection. Men between 40 and 60 are at the highest risk.
Symptoms of hip osteonecrosis
When blood flow is interrupted, the bone dies and can collapse — and, over time, the cartilage collapses with it, leading to debilitating arthritis.
People with AVN usually describe new-onset pain in the hip or groin. As the disease progresses, walking becomes difficult, and night pain is common. On examination, hip movements are often painful, particularly rotation.
It’s important to consider other causes of hip and groin pain, too — such as hip impingement, arthritis, dysplasia, or bone marrow oedema.
How is osteonecrosis of the hip diagnosed?
Imaging confirms the diagnosis, and early detection is critical.
- X-ray — in early cases, shows sclerosis (hardening) of the dead area of bone; in advanced cases, collapse of the femoral head and arthritis. An X-ray can be normal early on, which is why an MRI is often needed.
- MRI — the best test for AVN. It reveals bone swelling (oedema) in the femoral head well before X-ray changes appear, and shows later cartilage destruction and collapse.
Why early diagnosis matters so much. AVN is progressive. Once the femoral head collapses, the joint is damaged permanently and often needs replacement. Caught early — before collapse — there are joint-preserving options. So new, unexplained hip or groin pain, especially in someone with risk factors such as steroid use or high alcohol intake, deserves prompt imaging (an MRI) rather than watchful waiting.
How is osteonecrosis of the hip treated?
Treatment is complex, and depends heavily on the stage.
Early disease (before cartilage collapse):
- Conservative — rest with crutches and anti-inflammatory medication, to reduce load while blood flow recovers. A medication called a bisphosphonate (such as alendronate) is sometimes used, though the evidence is mixed.
- Joint-preserving surgery — core decompression (drilling one or more holes into the femoral head to improve blood flow), sometimes combined with a bone graft from a healthy site. A recent review found decompression plus bone grafting was better than decompression alone at preventing collapse — though it didn’t reduce the time to eventual hip replacement.
Advanced disease (after collapse):
- Total hip replacement — the best option once collapse has occurred. It gives good pain relief and works well for people over 40 with established collapse.
Frequently asked questions about osteonecrosis of the hip
What is the best exercise for avascular necrosis of the hip?
A programme combining strengthening and mobility. Strengthening should target the glutes, hamstrings, adductors, and hip flexors, and core exercises help stabilise the hip and pelvis. Aim for two to three sessions a week. Exercise should always be paired with proper medical management, because AVN requires staging and monitoring — it isn’t treated by exercise alone.
Do bisphosphonates prevent AVN from progressing?
The evidence is mixed. Bisphosphonates such as alendronate are sometimes used early to try to prevent collapse, but studies haven’t consistently shown they improve outcomes or avoid collapse compared with other treatments. More research is needed, so they’re used on a case-by-case basis rather than routinely.
Is osteonecrosis of the hip serious?
Yes — it’s a progressive condition that, untreated, leads to collapse of the femoral head and severe arthritis. But the outlook is far better when it’s caught early, before collapse, when joint-preserving treatment is still possible. That’s why prompt diagnosis is so important.
Can osteonecrosis of the hip be treated without a hip replacement?
Sometimes — if it’s caught early. Before the femoral head collapses, joint-preserving options such as core decompression (with or without a bone graft) can help. Once collapse has occurred, a hip replacement is usually the best option. The earlier it’s found, the more options there are.
Does cortisone cause osteonecrosis of the hip?
High-dose or prolonged steroid use is one of the recognised risk factors for AVN, along with heavy alcohol intake and several medical conditions. This doesn’t mean a single joint injection causes it — the association is mainly with substantial systemic steroid exposure — but it’s why steroid history is relevant when AVN is suspected.
Final word from Sport Doctor London about osteonecrosis of the hip
AVN, or avascular necrosis of the hip, is an uncommon but serious cause of hip or groin pain. Because it’s progressive, early diagnosis with an MRI — before the femoral head collapses — makes a real difference to the outcome and the treatment options. New, unexplained hip pain, especially in the presence of risk factors, should be assessed promptly.
If you have persistent, unexplained hip or groin pain, Dr Masci can assess you in London, including the right imaging. Contact the team here or call +44 (0) 203 488 0350.
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