Avascular necrosis of the hip
Avascular necrosis (AVN) of the femoral head occurs when the blood supply to the femoral head is disrupted, causing bone death, collapse of the joint surface, and progressive hip arthritis.
📊 Avascular necrosis of the femoral head accounts for approximately 10% of total hip replacements in the UK. It typically affects a younger patient population than primary osteoarthritis.
What is avascular necrosis of the hip?
Avascular necrosis (AVN) of the femoral head - also called osteonecrosis - occurs when the blood supply to the femoral head is interrupted, causing bone death. The necrotic bone loses its structural integrity and the femoral head may collapse, causing rapid destruction of the hip joint. The exact mechanism of vascular disruption varies by aetiology but the final common pathway is ischaemia of the subchondral bone.
The Ficat and Arlet classification (Stages 0-IV) grades AVN severity from normal X-ray with early MRI changes (Stage 0-I) to advanced femoral head collapse and secondary acetabular arthritis (Stage IV). Stage is the most important prognostic factor - early-stage disease may be stabilised by core decompression, while advanced collapse requires hip replacement. MRI is the most sensitive investigation for early diagnosis before X-ray changes are visible.
Bilateral AVN is common (up to 80% of cases have contralateral involvement at diagnosis) and must be assessed at initial presentation. The high rate of progression to femoral head collapse and the relatively young age of patients make AVN particularly challenging. Many patients require hip replacement within 5-10 years of diagnosis, and a young patient may require 2-3 revision procedures over their lifetime.
Common causes
- Corticosteroid use (the most common cause - even a short course can trigger AVN)
- Alcohol excess
- Hip fracture or dislocation (disrupting the blood supply acutely)
- Sickle cell disease and haematological disorders
- Radiation therapy to the pelvis
- Idiopathic (no identifiable cause in approximately 25%)
- Decompression sickness (caisson disease) in divers
Who is at risk? Corticosteroid use is the most important and preventable risk factor. High-dose or prolonged steroid use (as in SLE, organ transplant, asthma) significantly increases AVN risk. Alcohol excess is the second most common cause.
Symptoms
Symptoms vary depending on the severity and duration of the condition. Common symptoms include:
- Deep groin or hip pain, often of gradual onset
- Pain may be sudden and severe if femoral head collapse occurs
- Restricted range of movement, particularly internal rotation and flexion
- In early stages, symptoms may be minimal and the diagnosis made incidentally on MRI
- Bilateral symptoms in up to 80% of cases
When to seek help: See your GP if you have hip or groin pain and a history of corticosteroid use, alcohol excess, or previous hip injury. MRI should be arranged urgently in high-risk patients with hip pain as early diagnosis opens the window for joint-preserving treatment.
How is it diagnosed?
Your surgeon will take a detailed history and examine the joint. The following investigations may be arranged to confirm the diagnosis:
- X-ray - normal in early disease (Stages 0-I); shows crescent sign, flattening, and collapse in advanced disease
- MRI - gold standard for early diagnosis; shows characteristic double-line sign in the femoral head
- CT scan - assesses extent of bony collapse for surgical planning
- Bone scan - alternative to MRI but less sensitive
MRI should be arranged urgently in any patient with hip pain and risk factors for AVN (steroid use, alcohol, haematological conditions, previous hip trauma). The window for effective joint-preserving surgery is narrow and closes once significant femoral head collapse occurs.
Treatment pathway
Treatment is tailored to the severity of the condition, your age, activity level, and overall health. Most conditions are treated in a stepwise fashion, starting with the least invasive options.
Core decompression (with or without bone grafting)
Drilling of one or multiple channels into the necrotic femoral head to reduce intraosseous pressure and stimulate a healing response. Most effective in early-stage disease before collapse. May be combined with bone grafting or growth factor injection to enhance healing. Success rates of 50-75% in Ficat Stage I-IIa.
Total hip replacement
Once significant femoral head collapse has occurred (Ficat IIb or above), total hip replacement provides reliable pain relief. Outcomes in younger patients with AVN are slightly less durable than in older patients with primary OA, requiring careful implant selection and higher revision rates over a lifetime.
Analgesia, activity modification, and risk factor elimination
Cessation of corticosteroids (if medically possible) and alcohol. Analgesics and activity modification. Non-weight-bearing with crutches may slow progression in early disease but does not prevent collapse if blood supply is lost.
Recovery
Recovery after core decompression requires protected weight-bearing for 4-6 weeks. The patient requires long-term monitoring with X-rays and MRI to detect progression. Recovery after hip replacement follows the same timeline as for arthritis.
- Core decompression: crutches: 4-6 weeks
- THR mobilisation: Day 1
- Full recovery after THR: 6-12 months
- Long-term monitoring required for all stages:
What results can I expect?
Prognosis is closely related to stage at diagnosis. Early-stage disease treated with core decompression has 50-75% success in preventing progression. Advanced disease requiring hip replacement has good short-term outcomes but higher long-term revision rates in younger patients than primary OA.
Avascular necrosis of the hip - stages and treatment
In numbers
Typical activity timelines for this condition. These are approximate and vary considerably between patients. Always follow the specific guidance given by your surgeon and physiotherapist.
| Activity | Typical timeline | Notes |
|---|---|---|
| Address risk factors | Immediately | Reduce steroid dose where possible (with medical advice). Reduce or stop alcohol. Manage other underlying conditions.[1] |
| Image the other hip | At diagnosis | Both hips should be imaged at diagnosis, around 80% of AVN cases involve both sides at some point.[1] |
| Drive after core decompression | 6-8 weeks | When off crutches, comfortable in the car, and able to perform an emergency stop.[3] |
| Drive after hip replacement | 6-8 weeks | As for hip replacement for OA, when reactions and braking are safe.[3] |
| Return to work | 4-12 weeks | Depends on the procedure. Desk work earlier; manual or standing work usually 8-12 weeks.[1] |
| Ongoing monitoring | Long-term | After core decompression, X-ray and MRI follow-up monitor for progression. The other hip should also be checked.[1] |
Common concerns from patients with this condition or recovering from treatment, and whether they are expected or worth mentioning to your team.
Your questions, answered
Plain-English answers to the things people most often ask, grounded in UK clinical guidance. Tap a question to open it.
About thisWhat is avascular necrosis of the hip?
Avascular necrosis, also called osteonecrosis, is when the blood supply to the ball of the hip is reduced and a section of bone begins to die. Over time the weakened bone can collapse and the joint surface becomes irregular, leading to pain and arthritis.
CausesWhat causes it?
Common associations include high or prolonged steroid use, heavy alcohol intake, and injury such as a hip fracture or dislocation. It is also linked to some medical conditions, but in a proportion of people no clear cause is found.
SymptomsWhat does it feel like?
The usual symptom is groin pain that builds up, often worse on weight bearing and sometimes at rest or at night as it progresses. Early on the hip may feel relatively normal, which is why it can be missed without imaging.
TreatmentHow is it treated?
Treatment depends on how advanced it is. Caught early, before the bone collapses, joint-preserving options such as core decompression may be used to try to relieve pressure and stimulate healing. Once the joint surface has collapsed or arthritis has set in, a hip replacement is the usual and very effective solution.
OutlookDoes it always get worse?
Outcome depends on the size and stage of the affected area. Smaller, early lesions can sometimes stabilise, while larger ones involving the weight-bearing part of the ball are more likely to progress to collapse. Early specialist review gives the best chance of preserving the joint.
When to worryWhen should I seek advice quickly?
Worsening groin pain, a new limp, or difficulty bearing weight should be assessed without delay, particularly if you have known risk factors such as steroid use, so that any changes can be picked up while the joint can still be protected.
- 1.British Hip Society: Patient information
- 2.National Joint Registry annual report (NJR), hip and knee implant data
- 3.Royal College of Surgeons of England: Recovering from surgery, driving guidance
References are to UK clinical guidance and patient information from recognised organisations. This page is for general information and does not replace personalised advice from your own clinical team.
Preparing for surgery?
Read our step-by-step guide - what to expect before, during, and after your procedure.
How is it diagnosed?
- ✓X-ray - normal in early disease (Stages 0-I); shows crescent sign, flattening, and collapse in advanced disease
- ✓MRI - gold standard for early diagnosis; shows characteristic double-line sign in the femoral head
- ✓CT scan - assesses extent of bony collapse for surgical planning
- ✓Bone scan - alternative to MRI but less sensitive
Recovery milestones
- ●Core decompression: crutches: 4-6 weeks
- ●THR mobilisation: Day 1
- ●Full recovery after THR: 6-12 months
- ●Long-term monitoring required for all stages: