Avascular necrosis: symptoms, causes, treatment and outlook

Avascular necrosis means death of bone caused by a lack of blood supply. The Royal National Orthopaedic Hospital (RNOH) explains that AVN can happen when the blood supply to the ball of the hip is disrupted, either temporarily or permanently. Without blood, the affected bone and the tissue around it gradually begin to deteriorate. The bone itself can change shape, which is partly responsible for the joint stiffness people often experience, and it can result in hip osteoarthritis.

Alder Hey Children's Hospital describes AVN as the death of bone due to reduced or limited blood supply, which leads to scar tissue that stops any further healing, causing joint pain, loss of function and restricted movement. It says the joints most often affected are the hip, knee, shoulder, ankle or foot, wrist and elbow.

The RNOH calls AVN a condition that causes hip pain in young-to-middle-age adults. It is sometimes also called osteonecrosis, a name that refers to the same bone-death process.

The RNOH says some people have no symptoms in the early stages. As the condition worsens, affected joints might hurt only when putting weight on them, and eventually pain may be felt even at rest.

• Deep pain in the groin and/or buttock and side of the hip, which can sometimes spread down the thigh to the knee.

• Hip stiffness, which can cause difficulty putting on socks and shoes and cutting toenails.

• Pain at rest.

• Pain on walking, sometimes causing a limp.

• Pain on sitting, bending forwards or squatting.

• Hip pain and stiffness first thing in the morning.

The RNOH says there are many possible reasons for the blood supply to be disrupted, but in the majority of cases it is not possible to pinpoint an exact cause. A case with no clear cause is often called idiopathic. It can be linked with the following.

• Drinking too much alcohol.

• Using steroids, which may be needed, for example, in the management of cancer conditions or asthma.

• Sickle cell disease.

• Radiotherapy.

• Injury, such as a particularly bad fracture or a difficult bone infection.

The RNOH says hip AVN is diagnosed by X-ray. An X-ray will usually show AVN if it has been present for an extended period, but in the very early stages it may not show up even though you are having pain. In advanced stages the hip joint becomes very arthritic, and it may be hard to tell whether the main problem is AVN or advanced osteoarthritis of the hip; the treatment approach is then very similar.

In some cases you may have a bone scan or a magnetic resonance imaging (MRI) scan. Your doctor or surgeon uses these studies to plan the best treatment, looking at where the damage has occurred, the shape of the bones and whether osteoarthritis changes have developed.

For children with sickle cell disease, Alder Hey says bone or joint pain outside a sickle cell crisis should be reported to the sickle cell team, who will usually arrange an X-ray and sometimes an MRI.

Once AVN has occurred, the RNOH says treatment choices are determined by the changes within the hip joint and your symptoms, along with your age, activity level and general health. If AVN is detected early, non-surgical treatment may be an option, with the aims of relieving symptoms, preventing progression and improving function.

• Walking aids: a large aim of non-operative treatment is to decrease the load through the hip joint, usually with crutches or another aid that a physiotherapist teaches you to use.

• Education: understanding which movements and positions aggravate your symptoms and modifying them.

• Exercise: strengthening the muscles around the hip, maintaining movement in the joint and working on aerobic fitness. Water-based exercise or stationary cycling put less load through the hip.

• Weight management: extra weight puts more load through the hip joint, and losing weight could reduce pain.

• Painkillers: paracetamol can be used, and your doctor may prescribe stronger medicines or creams if needed.

• Surgery: the RNOH says medication may reduce pain but will not reverse AVN, and the main surgical option is a total hip replacement, which involves replacing the head of the femur and relining the socket. Physiotherapy starts on the day of surgery or the day after.

The RNOH suggests several ways to reduce the strain on the hip while you are under the care of your team. These are general measures and your physiotherapist can tailor them to you.

• Pace your activities: break them into smaller, more manageable chunks with regular rest breaks.

• Stairs: use a handrail, lead with the stronger leg going up and with the sore hip going down.

• Sitting: sit with the hips slightly higher than the knees, perhaps using a wedge cushion or higher chair, and avoid sitting for long periods.

• Equipment: aids exist, for example for putting on shoes and socks if bending the hip is difficult.

• Sleeping: a pillow between the knees can support the hips on your side, or a pillow under the knees on your back.

• Mood: living with pain can make people feel depressed, low or anxious, and a GP can offer advice and support or refer you to other services.

The RNOH points out that increased weight places more load through the hip joint and can aggravate symptoms, and that following a balanced, healthy diet together with regular exercise is a good start to losing weight. It also directs people to the NHS website for weight loss and for support with smoking cessation and lifestyle changes.

Alder Hey gives advice for children and families affected by sickle cell disease: exercise increases the circulation in the bone, with low-impact exercises such as walking and swimming being good, and a good calcium intake, including milk, cheese and yoghurt, is encouraged to help reduce the risk.

Alder Hey explains that sickled cells can clump in the single large blood vessel that supplies many joints, which is why sickle cell disease carries a risk of AVN. It says AVN usually affects older people with sickle cell disease but can start in late childhood and adolescence, with approximately 41% of adult patients getting AVN and 27% of children, citing a 2005 review in the British Journal of Haematology.

The main sign is bone pain that is there even when the child is not having a crisis, usually in the joint between the hip and thigh bone and felt when walking, with reduced range of movement, a slight limp or clicking, and sometimes numbness or tingling if the bone compresses a nerve. Management starts with pain medicines and physiotherapy. If the bone is severely affected a doctor specialising in bones becomes involved, and some types of AVN need surgery and joint replacement.

See your GP if you have persistent pain in the groin, hip, buttock or other joint, especially if it is worse on weight-bearing, is there at rest, or comes with stiffness or a limp, or if you have a risk factor such as long-term steroid use, heavy alcohol intake or sickle cell disease. Very early AVN may not show on an X-ray, so ask about further imaging if pain continues.

If you have sickle cell disease and bone or joint pain that is not part of a crisis, the guidance from Alder Hey is to tell your sickle cell team, who can arrange imaging. Speak to a GP too if living with pain is affecting your mood.

On the NHS, AVN is usually suspected by a GP and confirmed with imaging, with care led by orthopaedic surgeons and physiotherapists, and haematology teams where sickle cell disease is involved. Physiotherapy, walking aids and weight-management support are part of the non-surgical approach described by the RNOH, and joint replacement is offered when surgery is the right option.

Some people arrange a private scan or orthopaedic opinion to be seen sooner. The investigations and treatment options are the same; ask for results and plans to be shared with your GP.