Avascular necrosis of the hip (also called osteonecrosis of the hip) is a painful condition in which a loss of blood supply to the top of the thigh bone (femur) causes it to weaken and collapse.
The condition can affect anyone, but it is more common among men and people aged between 30 and 50.
In many cases, the condition is caused by an injury to the hip area (known as traumatic avascular necrosis), such as a hip fracture. However, it can also occur without any injury (known as non-traumatic avascular necrosis).
Avascular necrosis of the hip is a serious condition that needs emergency treatment by a bone and joint specialist (orthopaedic surgeon) to help prevent it getting worse.
Avascular necrosis of the hip often has no symptoms in its early stages. However, as it progresses and the bone begins to collapse, it tends to become painful.
Pain may be felt in one or both hips or groin, and it may move into the buttocks, knees and/or the thighs. It may feel worse on standing and walking, and get better with rest. As the condition gets worse, pain may even occur at rest and become deep and throbbing in nature.
In rare cases, you may have no pain at all.
You may also develop a limp.
There are two types of avascular necrosis of the hip:
- traumatic: following an injury
- non-traumatic: without direct injury
Traumatic avascular necrosis of the hip
Traumatic avascular necrosis of the hip is the most common. It arises when an injury interrupts the blood flow to the upper end of the thigh bone which forms part of the hip joint.
Causes of traumatic avascular necrosis include:
- hip fracture
- hip dislocation
- previous hip surgery
Non-traumatic avascular necrosis of the hip
The specific cause of non-traumatic avascular necrosis of the hip is not fully understood, but there are several factors which can increase your risk of developing the condition. These include:
- alcohol misuse
- Cushing’s syndrome
- sickle cell anaemia
- blood clotting disorders
- HIV infection
- autoimmune disorders like lupus and vasculitis
- liver, pancreas or kidney disease
- genetic conditions such as Gaucher’s disease
- decompression sickness (due to high atmospheric pressure e.g. deep sea diving)
- high blood fat (lipid) levels or a tendency to develop fat emboli (lumps of fat that cause a blockage of blood flow)
Medical treatment for other conditions
The two most common factors are steroid medication and alcohol misuse.
Diagnosis of avascular necrosis of the hip
Your doctor may suspect a diagnosis of avascular necrosis of the hip based on your symptoms, medical history and an examination of your hip.
Your doctor or orthopaedic surgeon is also likely to organise imaging tests, such as:
- an X-ray - helpful in more advanced stages
- MRI scan - especially in early stages
- a special bone scan
Blood tests may be done to detect any underlying disorders such as blood clotting abnormalities.
There are several ways you can reduce your risk of getting avascular necrosis of the hip.
- eating foods that contain lots of calcium and vitamin D, such as milk, cheese, green leafy vegetables and oily fish
- avoiding smoking
- drinking no more than 14 units of alcohol each week
- if you take steroid medicines, working with your doctor to take the lowest dose for the shortest possible time
- reducing your risk of falls and fractures by keeping walkways clear, watching out for slippery floors, wearing sturdy shoes and having your eyes checked
- closely following rules for decompression during diving and when working in pressurised environments
Avascular necrosis of the hip is a serious condition that needs to be treated quickly to prevent a complete collapse of the hip joint. However, it is still not clear how best to manage avascular necrosis of the hip.
The management you receive will likely depend on several factors, such as the cause, severity and progression of the condition.
Avascular necrosis management options can be divided into:
- non-surgical management
Non-surgical management helps to relieve pain but generally does not help to stop the condition from getting worse. The various non-surgical management options include:
- taking weight off the hip joint by limiting activity and using crutches
- taking medicines that prevent bone loss or improve blood flow to the hip. For people with blood clotting problems, for example, blood thinners can help prevent blood clots that can block the blood supply to the bone
Research into the use of possible complementary therapies, such as extracorporeal shockwave therapy (ESWT), pulsed electromagnetic fields and high-pressure oxygen treatment, is ongoing.
There are several types of surgery which can slow down or even prevent avascular necrosis from getting worse. If you require surgery, your doctor will work with you to decide which type is best for you.
There are surgical procedures which aim to preserve the hip joint. These are particularly effective in the earlier stages of the condition.
The surgical options include:
- core decompression – small areas of damaged bone tissue are removed to reduce pressure in the bone, which can reduce pain and stimulate bone healing
- bone graft – the damaged bone is replaced with healthy bone (sometimes with blood vessels and stem cells) from another part of your body
- osteotomy – changing the position of the top of the thigh bone (which forms part of the hip joint), so that the weight of the body is distributed through a healthy area of the top of the thigh bone and not through the damaged part.
If the bone has collapsed, you may need a hip replacement to reduce any pain and improve your hip movements.
Avascular necrosis of the hip can lead to complete collapse of the joint if it is left untreated. If you think you have symptoms of avascular necrosis of the hip, or are unsure, see your doctor immediately.
If you have suffered from avascular necrosis of the hip, you may find it helpful to share your experience with others who have had the condition. Ask your doctor for information about useful support groups.
To find answers to any other health questions you might have, visit our Health A-Z.
If avascular necrosis of the hip is left untreated, over time it can lead to permanent hip joint damage and collapse. It may also cause osteoarthritis of the hip.