Avascular necrosis (AVN)

What is avascular necrosis?

Avascular necrosis occurs when a bone or joint loses its blood supply, causing it to die. This makes the bone brittle and weak, often leading to fractures which can cause deformity and collapse.


Also known as osteonecrosis, it can occur in any bone in the body. Commonly avascular necrosis occurs in the hip joint causing acute and severe pain.

What causes avascular necrosis?

Avascular necrosis occurs when a bone does not receive an adequate blood supply. This can result from:


Injury to the bone or joint (such as dislocation or a fracture) can disrupt blood flow.

Advanced osteoarthritis

The final stages of advancing arthritis may involve AVN and collapse of the joint, most often seen in the hip and knee. 

Lifestyle factors

Long term excessive use of alcohol and smoking may trigger the condition.


Steroid medications used to treat other diseases may have a side effect of causing avascular necrosis. 

Blood diseases

Conditions of the blood like sickle cell anaemia and Gaucher’s disease can cause bones to receive less blood.

Cancer treatments

Some radiation treatments can weaken the bones and blood vessels, making them more prone to damage.

What are the symptoms of avascular necrosis?

Early stages of avascular necrosis often have no symptoms at all. You may not notice anything until the condition worsens.


As this happens, you may feel pain when moving the joint or during load bearing activities. The affected area may eventually become painful even when you aren’t moving. When it develops in the hip, this pain usually centres on the groin, thigh, or buttock.

How do you diagnose avascular necrosis?

After discussing your medical history and any risk factors, your doctor will perform a physical examination to diagnose AVN. This involves moving the affected joint in different ways to test its range of motion and when pain is produced.  

If avascular necrosis is suspected, your doctor will usually ask for x-rays and possibly a bone scan. This helps confirm the diagnosis and assess the severity of the condition so it can be treated effectively. The doctor may also request an MRI or other tests to see soft tissue in the area.

Treating avascular necrosis

Treating avascular necrosis involves two aspects: managing the weakened bone and addressing the underlying cause. Depending on the severity, a number of approaches may be used.


These include:



Physiotherapy for avascular necrosis aims to maintain joint mobility and strengthen the muscles around the affected joint. It often follows surgery and supplements other treatments.



Paracetamol and anti-inflammatories are initially used to manage pain symptoms.  With true joint collapse, stronger medications may be required.


Core decompression

Core decompression is a procedure to remove the inner layer of the bone. This is particularly used around the hip joint. The procedure allows new bone tissues and blood vessels to grow around the joint.



Osteotomy is a surgical procedure which changes the shape of the bone in the affected area.  It may help restore blood flow, affect the way the joint moves, or remove a damaged area of bone.  The is of particular use around the knee.


Joint replacement

Joint replacement surgery may be recommended if AVN has caused the joint to deteriorate past the point of restoration.

Joint replacement involves removing the joint and replacing it with a prosthetic, which can help reduce pain and restore function. Dr Jason Ward is an expert in hip and knee replacement surgery with a muscle-sparing anterior approach for hips.  He offers robotic knee replacements as well as traditional approaches.

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