Avascular Necrosis

Author David Slattery

FRACS (Orth), MBBS(Hons), LLB, FAOrthA — Orthopaedic Surgeon

What is Avascular Necrosis of the Hip?

Avascular necrosis (AVN), also called osteonecrosis, is a condition in which the blood supply to the head of the femur (the “ball” of the hip joint) becomes impaired. Bone is living tissue that requires a continuous blood supply; when this is disrupted, the bone cells begin to die. Over time, the weakened bone can collapse, damaging the smooth surface of the joint and leading to pain and arthritis.

AVN can affect people across a wide range of ages, including younger adults, and early diagnosis is important because treatment options are broader before the bone has collapsed.

Anatomical diagram of the hip joint labelling the pelvis, acetabulum (socket), labrum, femoral head (ball) and femur
AVN affects the femoral head — the ball of the ball-and-socket hip joint. When its blood supply is disrupted, the bone weakens and can collapse.

Causes and Risk Factors

AVN occurs when the blood supply to the femoral head is interrupted. Recognised causes and risk factors include:

  • Previous hip injury, such as a fracture or dislocation
  • Long-term or high-dose corticosteroid use
  • Significant alcohol intake
  • Certain medical conditions affecting blood or blood vessels
  • Some other underlying conditions and treatments

In some cases no clear cause is identified. Identifying any contributing factors is part of the assessment, as it may influence management.

Symptoms

  • Pain, often felt in the groin, and sometimes the thigh or buttock
  • Pain that initially occurs with weight-bearing and activity
  • Progression to pain at rest as the condition advances
  • Stiffness and reduced range of motion
  • A limp or difficulty walking in more advanced disease

In its earliest stages AVN may cause few or no symptoms and can be detected incidentally on imaging performed for another reason.

Diagnosis

Diagnosis is based on the history, risk factors, and a clinical examination, supported by imaging. X-rays may appear normal in early disease but show changes as it progresses. MRI is particularly valuable because it can detect AVN at an early stage, before changes are visible on X-ray, and helps determine the extent of the affected bone. Staging the condition guides treatment.

Four-stage progression of hip osteonecrosis, from a healthy hip to collapse of the femoral head
Osteonecrosis progresses from a normal, healthy hip (Stage I) to collapse of the femoral head (Stage IV).

Treatment Options

Treatment depends on the stage of the condition — particularly whether the femoral head has collapsed — as well as the size and location of the affected area, your symptoms, and your individual circumstances.

Earlier-stage options (before collapse)

When AVN is identified before the bone has collapsed, treatment may aim to preserve the joint. Options can include managing any contributing factors, and joint-preserving procedures intended to support the bone or improve its blood supply, where appropriate.

Core decompression of the hip — diagram and x-ray showing the drill hole pathway in the femoral head
Core decompression: small drill holes into the affected area of the femoral head.
A tantalum rod supporting the diseased femoral head to prevent collapse
A tantalum rod may be used to support the bone and resist collapse.

Later-stage options (after collapse)

Once the femoral head has collapsed and the joint surface is damaged, joint preservation is generally no longer effective, and hip replacement becomes the most reliable option for relieving pain and restoring function.

Total hip replacement with both the femoral head and the socket replaced
In a total hip replacement, both the femoral head and the socket are replaced.

The most appropriate approach depends on the stage and individual factors, and will be discussed with you at your consultation.

Recovery and Outlook

The outlook depends greatly on the stage at which AVN is treated. Early diagnosis offers the best opportunity for joint-preserving treatment, while advanced disease is effectively treated with hip replacement. Recovery depends on the specific treatment undertaken and will be explained according to your circumstances.

Frequently Asked Questions

Why is early diagnosis of AVN important?

Before the femoral head collapses, there may be options aimed at preserving the natural joint. Once collapse has occurred and the joint surface is damaged, these options are generally no longer effective. Early diagnosis therefore widens the range of possible treatments.

Can avascular necrosis be cured without a hip replacement?

In earlier stages, joint-preserving treatments may be possible in appropriate cases. Whether the joint can be preserved depends on the stage, the size and location of the affected area, and individual factors. In advanced disease, hip replacement is usually the most reliable treatment.

Does AVN always lead to hip replacement?

Not always. The course varies between individuals and depends on the stage at diagnosis and the response to treatment. Some patients with early disease may avoid or delay replacement, while others with advanced disease benefit from it.

Medical Disclaimer
The information on this page is intended as general patient education and does not constitute medical advice. Every patient is different, and treatment decisions should always be made in consultation with a qualified medical professional based on your individual circumstances, health history, and imaging. Outcomes from treatment vary between patients and cannot be guaranteed. If you have concerns about your hip health, please contact Dr Slattery’s rooms to arrange a consultation.

Contact Dr David Slattery.

Contact Dr David Slattery’s rooms to book an appointment or speak with our team about referrals, availability, and treatment options.