Ankylosing spondylitis

Ankylosing spondylitis (AS) is a form of arthritis. It mainly affects the lower back. Other joints and other parts of the body are sometimes affected. Treatment includes regular exercise and anti-inflammatory drugs. The severity of AS varies from mild to severe. It is mild or moderate in most cases. About 8 in 10 people with AS remain fully independent or minimally disabled in the long term and are able to work full-time for the whole of a normal working life. One important point to remember - tell a doctor urgently if you have AS and develop a painful or red eye. An eye complication of AS called uveitis can be serious but can be treated successfully if treatment is given promptly.


Understanding the lower back

The spine is made up of many bones called vertebrae. The vertebrae are roughly circular and between each vertebra is a 'disc'. The discs are made of strong rubber-like tissue which allows the spine to be fairly flexible. Strong ligaments also attach between adjacent vertebrae to give extra support and strength to the spine. There are also various muscles that are attached to the spine which enable the spine to bend and move in various ways. There are also small facet joints that help to attach vertebrae to each other. The sacrum is formed from five fused vertebrae that are joined together. They form a triangular shaped structure at the bottom of the spine. The two sacro-iliac joints are the large long joints that join the sacrum to the ilium (the main bone of the pelvis).

The spinal cord, which contains the nerves that come from the brain, is protected by the spine. Nerves from the spinal cord come out from between the vertebrae to take and receive messages to various parts of the body.

What is ankylosing spondylitis?

Ankylosing spondylitis (AS) is a chronic (persistent) rheumatic (arthritic) disease of unknown cause. It mainly affects the spine and the sacro-iliac joints. Sometimes other joints and other parts of the body are affected. The word spondylitis means inflammation of the spine. The word ankylosing means bones that tend to join together (fuse) across a joint.

The lower back is typically the main site of inflammation in AS

The ligaments of the lower spine become inflamed at the points where they attach to the spinal vertebrae. In time, this can stimulate the bone making cells and cause some bone to grow and form within the ligaments. In time, these bony growths may become larger and form bony 'bridges' between adjacent vertebrae. This may, over time, cause some of the vertebrae in the spine to fuse together with this new abnormal bone material.

The sacro-iliac joints and their nearby ligaments are also commonly affected with inflammation. This too may ultimately end in a 'fusion' between the sacrum and pelvis. The small facet joints of the spine are also commonly inflamed.

Other areas of the body may be affected

The disease is not always confined to the spine and sacro-iliac joints. In some cases, inflammation occurs in other joints and in other parts of the body outside of the spine (detailed below).

Who gets ankylosing spondylitis?

AS most commonly begins between 15 and 35 years of age, but also occurs in children and older adults. It is 3-5 times more common in men than women. There may be a family history with two or more members of a family being affected. About 1 in 1000 people in the UK develop AS at some point in their life.

What causes ankylosing spondylitis?

The cause is not known. However, there is a strong genetic (hereditary) tendency. For example, there is a strong association with a gene called HLA-B27. About 9 in 10 in people with AS have this gene compared with less than 1 in 10 in the general population. However, having this gene does not mean that you will automatically get AS. Many people have this gene and do not develop AS. Also, some people develop AS who do not have this gene. It is thought that something may 'trigger' AS to develop in people who have an inherited tendency to develop AS, and the gene HLA-B27 provides a strong tendency. However, the 'trigger' is not known and other genes and factors may also be involved in causing AS.

What are the symptoms of ankylosing spondylitis?

Back pain

The main symptom is back pain. The pain usually starts in the lower back. You may think of it as just mild backache at first. It typically becomes gradually worse over several months. You may have pain over your buttocks, and down the back of your thighs. The buttock pain may be felt sometimes on one side and sometimes on the other side. Coughing or straining may make pain worse. Rest does not make it better. In fact, the pain may wake you from sleep. Instead, exercise and movement usually eases the pain. (This is the opposite to most bouts of common mechanical backache which may alert a doctor to the diagnosis of AS.) The pain tends to be worse first thing in the morning. Lying in bed after waking is often uncomfortable. The pain tends to ease as the day goes on.

The middle (chest part) of the spine may become affected. If this occurs the joints between the ribs and the spine may also become painful.

Stiffness in the lower spine

The stiffness can be quite severe first thing each morning. It usually improves with activity and exercise, and tends to ease as the day goes on.

Other joint symptoms apart from the spine

Other joints are affected at some stage in about 4 in 10 cases. The most common are: the hips, knees, ankles, and shoulders. Affected joints can become painful, stiff, and swollen.

Inflammation of tendons and ligaments

Tendons and ligaments in various parts of the body (in addition to those attached to the vertebrae of the lower spine) may become inflamed and painful where they attach to bones. Common examples are the Achilles' tendon where it attaches to the heel, and where chest muscles attach to the ribs.

Inflammation of part of the eye (uveitis)

This affects about 1 in 3 people with AS from time to time. Tell a doctor urgently if you have AS and develop a painful or red eye. If you develop uveitis, treatment with eye drops should be started as soon as possible after eye symptoms begin. Treatment of uveitis is usually successful. However, if not treated quickly there can be permanent loss of vision in the eye (partial or complete).

General symptoms

Some people with AS feel generally unwell with symptoms of tiredness or depression. Weight loss or anaemia sometimes occur.

Associated diseases

Some other conditions develop more commonly than normal in people who have AS. For example, people with AS have a greater than average chance of developing ulcerative colitis, Crohn's disease, psoriasis, osteoporosis, lung fibrosis, cardiovascular disease (see later) and heart valve problems. Note: most people with AS do not get these conditions - it is just that they are more common in people with AS than would be expected in the 'general population'.

How is ankylosing spondylitis diagnosed?

The diagnosis is usually made by the typical symptoms. However, it can be difficult for a doctor to confidently diagnose AS in the early stages of the disease as symptoms can develop very gradually. For example, mild low back pain may develop 'on and off' for several months. As back pain from 'straining the back' is very common, it is often difficult to tell the difference between this common 'mechanical' backache and AS. It may take months, and sometimes years, for the symptoms to develop more fully and the correct diagnosis of AS to be made.

Blood tests, HLA B-27 tests, MRI/CT scan

As the disease progresses, typical changes develop on X-ray pictures of the sacro-iliac joints and spine. The X-ray pictures show the bones gradually fusing together. However, these changes may take several years to become bad enough to be seen on X-ray pictures.

Until recently, the X-ray changes were the only way to confidently confirm AS. More recently, an MRI scan of the sacro-iliac joints has been used to confirm the diagnosis at an earlier stage. An MRI scan can give a much more detailed view of a joint than a traditional X-ray picture and can detect inflammation in the sacro-iliac joints.

How does ankylosing spondylitis progress?

Symptoms can vary in severity and usually wax and wane. Flare-ups of inflammation which cause periods of worse pain and stiffness tend to occur from time to time. If joints outside your spine are affected, they tend to flare up at the same time as back symptoms. The number of flare-ups that occur, how severe they are, and how long they last, can vary greatly from person to person.

In time, the mobility and flexibility of your spine may be reduced. This occurs as the inflammation and bony growths that occur cause gradual 'fusion' (joining together or ankylosis) of some of your vertebrae. The number of vertebrae involved and the extent of any fusion varies from person to person. A stooping (bent-over) deformity may occur in severe cases.

What are the treatments for ankylosing spondylitis?

The aims of treatment are: to ease pain and stiffness, to keep your spine as mobile and flexible as possible, and to limit the extent of any deformity.


It is vital to have a good posture and a regular exercise routine. This helps you to keep a full range of spinal movement and may help to prevent your spine from 'stiffening up'. Regular specific exercises are thought to limit the extent of any spinal deformity that may develop. The exercises may also ease back pain. You will normally be referred to a physiotherapist who will advise on the exact exercises to do. Exercises should become a routine part of life. Ideally, they should be done daily.


Anti-inflammatory drugs

Anti-inflammatory drugs reduce inflammation and ease pain. Their correct name is 'non-steroidal anti-inflammatory drugs' (NSAIDs). An important reason to take these drugs is to ease pain so that you can do regular exercises without much discomfort.

It is generally thought that anti-inflammatory drugs only ease symptoms but do not alter the course of the disease. Therefore, advice had been to take courses of these drugs 'as and when' the pain flares up. But then if symptoms ease, not to take them. However, one recent research study has suggested that regular long-term use of anti-inflammatory drugs may slow down the progression of AS. Further studies are needed to confirm this.

There are several different anti-inflammatory drugs. For example, ibuprofen, diclofenac and naproxen - but there are many others. If one does not suit, another may be fine. Side-effects sometimes occur with these drugs. For example:

    • Stomach pain and bleeding from the stomach are the most serious. The risk of this is higher if you are over 65, or have had a duodenal or stomach ulcer. In some situations, your doctor may prescribe another drug to 'protect the stomach' from these possible problems. If you develop abdominal (stomach) pains, pass blood or black stools, or vomit blood whilst taking anti-inflammatory drugs, stop taking the tablets and see a doctor urgently.

    • You may not be able to take anti-inflammatory drugs if you have asthma, high blood pressure, kidney failure, or heart failure.

The leaflet which comes with the tablets gives a full list of possible side-effects.

Ordinary painkillers

Painkillers such as paracetamol may be sufficient if symptoms are mild between flare-ups. (But note the comment above about the possible benefits of taking long-term anti-inflammatory drugs.) You can also take paracetamol in addition to an anti-inflammatory drug for top-up pain relief.

Immunosuppressant drugs

Newer powerful drugs have become available in recent years that suppress the immune system. These have made an impact on the treatment of AS. They tend to be divided into two groups, biological therapies and immunomodulators.

Biological therapies: These are genetically engineered proteins such as special antibodies called monoclonal antibodies. They can target specific chemicals of the immune system involved in the inflammation process. In AS, a chemical called cytokine tumour necrosis factor alpha (TNF-alpha) is involved in the inflammation process. Certain drugs in a group called TNF-alpha antagonists (which are really manufactured antibodies) block the action of this chemical and therefore suppress the disease activity. TNF-alpha antagonists include etanercept, adalimumab and infliximab. Treatment with one of these drugs is an option in some cases. These drugs need to be given by injection every 1-6 weeks depending of the dose and type and require special monitoring as some people develop serious side-effects. For example, taking these drugs can make you more prone to develop a serious infection. A specialist may advise using one of these drugs if you have moderate or severe AS which has not been helped much by anti-inflammatory drugs.

Regarding TNF antagonists, recent national guidelines from the National Institute for Health and Clinical Excellence (NICE) states:

"Adalimumab or etanercept are recommended as possible treatments for people with severe ankylosing spondylitis who:

    • have active spinal disease as assessed on two occasions 12 weeks apart, and

    • have tried at least two non-steroidal anti-inflammatory drugs (NSAIDs) but they have not worked.

Treatment should be started and supervised by a specialist who is experienced in diagnosing and treating ankylosing spondylitis. People taking adalimumab or etanercept should have regular check-ups. Treatment should continue only if the person's ankylosing spondylitis shows an adequate improvement. If the improvement is not maintained or if the drug stops working then treatment should be stopped. Infliximab is not recommended."

Immunomodulators: These are drugs that modify and suppress the immune system. They include sulphasalazine and methotrexate. (These drugs are commonly used to treat people with rheumatoid arthritis - a different type of arthritis.) One may be tried in people with severe AS where other treatments have not helped much. Research continues to clarify their role in AS. However, as a rule, research studies suggest that they do not work as well in AS as they do in rheumatoid arthritis. People who take these drugs need careful monitoring as there is a risk from serious side-effects. For example, taking these drugs can make you more prone to develop a serious infection. A specialist can advise on the up-to-date research relating to these drugs and if one should be used.

Other medication

Occasionally, other drugs are sometimes used:

    • A steroid injected directly into a badly inflamed joint is sometimes used to ease symptoms.

    • Drugs called bisphosphonates have shown promising results in research trials. Further research is needed to clarify their role in the treatment of AS.


    • TENS machines are sometimes used to ease pain. (These give tiny electrical currents into the affected area.)

    • Heat, for example, a hot shower, may help to ease pain, particularly each morning.

    • Some people find regular massage is soothing.

    • About 1 in 20 people with AS need a hip replacement at some stage as their hip sometimes becomes badly affected. Rarely, surgery is needed to correct a severe spinal deformity.

Ankylosing spondylitis and heart disease

If you have AS you have an increased risk of developing cardiovascular disease when you become older. (Cardiovascular disease refers to narrowing of the arteries by a fatty substance called atheroma. This may eventually lead to angina, heart attack or stroke.) It is not clear why the risk is increased in people with AS. It may be that the chronic (persistent) inflammatory nature of the condition is partially responsible. Therefore, you should consider doing what you can to reduce the risk of heart disease by other means.

For example, if possible:

    • Eat a good healthy diet.

    • Exercise regularly.

    • Lose weight if you are overweight.

    • Do not smoke.

    • If you have high blood pressure, diabetes, or a high cholesterol level, they should be well controlled on treatment.

See leaflet called 'Preventing Cardiovascular Disease' for details.

What is the outlook (prognosis)?

Although there is no cure for AS, the outlook is quite good for most people with the disease. After an initial period of inflammation, in many people with AS the disease settles down to a low level of activity. Flare-ups of symptoms occur from time to time, but are often mild or moderate. In most people with AS, regular exercise and medication keep symptoms away, or much reduced. The lower spine tends to become more stiff and less flexible over the years. In some people, the stiffness is more severe than in others.

About 8 in 10 people with AS remain fully independent or minimally disabled in the long term. This is despite eventual severe restriction of spinal flexibility that occurs in about 4 in 10 people with AS. Most people with AS are able to work full-time for the whole of a normal working life. However, heavy manual work may become difficult. If spinal deformities do arise, they do so after at least 10 years.

About 1 in 10 people with AS have a severe form of the disease, and may become quite disabled over time. However, the recent introduction of treatment with TNF-alpha antagonists (described above) seems to have improved the outlook for people with more severe AS.

In most cases, episodes of arthritis outside the spine and/or eye inflammation do not occur, or only occur now and again. In a small number of cases these problems outside the spine recur frequently, or become severe. Uveitis (eye inflammation) may lead to blindness if not treated promptly.

People with established AS have an increased risk of fracturing the spine if they are involved in a high impact accident such as a car crash. This is because the spine becomes more easy to fracture as it becomes more stiff and rigid.

Further help and information

The National Ankylosing Spondylitis Society

Unit 0.2, One Victoria Villas, Richmond, Surrey, TW9 2GW

Tel: 020 8948 9117 Web:

Provides information and support. For example, the society has a network of over 90 centres in the UK that provide weekly exercise sessions supervised by a physiotherapist. They also publish and sell an audio cassette and a home-exercise video.

Arthritis Research Campaign - ARC

Copeman House, St Marys Court, St Marys Gate, Chesterfield, Derbyshire, S41 7TD.

Tel: 0870 850 5000 Web:

Arthritis Care

18 Stephenson Way, London, NW1 2HD

Helpline: 0808 800 4050 Web: