Hip condition
Avascular necrosis — osteonecrosis — is bone dying from a lost blood supply, and in the hip it follows a timetable that has very little to do with how much it hurts. The bone weakens quietly, then the round head of the femur flattens, and everything changes at that moment: before collapse there is a real prospect of saving your own hip, and after it the honest answer is a replacement. The whole of this page is about that window, and how not to spend it waiting.
Tap any that apply to you — this is guidance, not a diagnosis, but it tells you how quickly to act.
That combination deserves imaging soon rather than eventually. Avascular necrosis is diagnosed on MRI, and an X-ray that looks normal does not rule it out. A sudden step up in pain after weeks of ache can mean the bone beneath the surface has given way — the point at which the options narrow considerably.
None of the classic risk factors, which is reassuring. Unexplained groin pain still deserves a proper diagnosis, since several hip conditions present the same way and the treatments differ sharply. Worth an assessment rather than a wait-and-see.
The head of the femur is fed by a small set of vessels running along the neck of the bone, with very little in reserve if they are interrupted. That anatomy is why this joint accounts for most cases of osteonecrosis in the body:
Two facts drive everything about this condition. The first is that an X-ray is often normal in early avascular necrosis — the bone has died but has not yet changed shape, so the film looks unremarkable while the process is well underway. MRI shows it long before an X-ray can, which is why a normal X-ray is not an all-clear when the story fits. The second is that the joint surface only has to fail once. While the head of the femur is still round, treatment can aim at preserving your own hip. Once it has flattened, the cartilage above it is destroyed by the collapse beneath, and no operation restores that shape — which turns a joint-preservation problem into a joint-replacement one. Between those two facts sits the reason this page pushes harder than the others on our site: the period when treatment can change the outcome is also the period when symptoms are mildest, and mild symptoms are exactly what people wait out. If you have the risk factors and unexplained groin pain, the imaging is worth doing now. And if one hip is affected, the other is checked, because in a large share of cases both are involved even when only one hurts.
The stage decides the treatment more than the symptoms do — tap where you are:
Then the priority is an MRI, not a wait. An X-ray alone cannot exclude early avascular necrosis, and the earliest stages are where treatment has the most to offer. If you carry any of the recognised risk factors, that scan is the single most useful thing you can do this month.
This is the window — and it is worth acting inside it. With the head still round, treatment aims at saving your own hip: addressing any underlying cause, protecting the joint, and surgery to relieve pressure within the bone and encourage new vessels in. Decisions here are time-sensitive rather than urgent.
Once the surface has collapsed, the honest conversation is about replacement. That is not a failure — hip replacement for avascular necrosis performs very well, including in younger patients, and it reliably restores what the collapse took away. The other hip is still worth imaging.
Avascular necrosis treatment divides cleanly at the moment of collapse:
Tap each card to reveal the truth:
Avascular necrosis, also called osteonecrosis, is the death of bone tissue caused by an interrupted blood supply. The ball of the hip is particularly vulnerable because it is fed by a small and precarious set of vessels. When that supply fails, the bone beneath the joint surface weakens, and if enough of it gives way the round head of the femur flattens. The cartilage above it is healthy at first — it fails only because its foundation does.
Sometimes an injury: a hip fracture or dislocation can tear the vessels directly. More often it follows something systemic — long courses of certain prescribed medicines taken for other illnesses, heavy alcohol intake over years, sickle cell disease, lupus and related autoimmune conditions, treatment for cancer, organ transplantation, clotting disorders, or the decompression illness divers face. In a proportion of cases no cause is ever identified.
It depends almost entirely on one thing: whether the head of the femur has collapsed yet. Before collapse, the aim is to save your own hip — addressing the underlying cause where one exists, protecting the joint, and surgery that relieves pressure within the bone to encourage new blood vessels to grow in. After collapse, the joint surface can no longer be restored, and hip replacement becomes the reliable answer.
Small lesions found early, particularly where the cause has been removed, occasionally stabilise or repair. Most do not. Left alone, a significant proportion progress to collapse of the femoral head within two to three years, and the process is not usually reversed by rest. This is why avascular necrosis is monitored actively with repeat imaging rather than simply watched for worsening pain.
No — but the odds depend on when it is caught. Hips treated before the surface collapses have a genuine chance of being preserved, and many people go years without further surgery. Once the head has flattened, joint-preserving options largely close and replacement becomes the operation that reliably restores comfort and function. Modern hip replacement performs very well in this group, including in younger patients.
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