Ankylosing Spondylitis – A Guide

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Ankylosing spondylitis (AS) is a type of chronic (long-term) arthritis that affects parts of the spine, including the bones, muscles and ligaments.


Most people with ankylosing spondylitis experience back pain and stiffness. The condition can be severe, with around 1 in 10 people at risk of long-term disability.

The spine

The spine is made up of a column of interlocking bones called vertebrae. The vertebrae are supported by muscles and ligaments that control the movements of the spine. See the box (left) for more information about the spine.

In ankylosing spondylitis, the spinal joints and ligaments and the sacroiliac joints (the joints at the base of the spine) become inflamed. Inflammation in the spine can cause pain and stiffness in the neck and back. Sacroiliitis (inflammation of the sacroiliac joints) causes pain in the lower back and buttocks.

How common is ankylosing spondylitis?

Ankylosing spondylitis can develop at any time from the teenage years onwards. It is three times more common in men than in women. The condition usually occurs between 15 and 35 years of age, and rarely starts in old age.

Estimates of different European populations suggest that ankylosing spondylitis may affect between 2-5 adults in every 1,000. In the UK, around 200,000 people have been diagnosed with ankylosing spondylitis.


There is no cure for ankylosing spondylitis. However, the condition can be treated with:

  • physiotherapy where physical methods, such as massage and manipulation, are used to improve comfort and spinal flexibility
  • medication helps to relieve pain and control the symptoms

The progression of ankylosing spondylitis varies among people. It is estimated that 70-90% of people will remain independent and only minimally disabled by the condition.

After around 10 years the inflammation may make the neck and back rigid. This process is called ankylosis. In some people who have severe, long-standing ankylosis, their rib cage (chest) can also become stiff and inflexible.

See Ankylosing spondylitis – complications for more information about the various complications that the condition can cause.


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Symptoms of ankylosing spondylitis

The symptoms of ankylosing spondylitis (AS) vary greatly from person to person, but they usually take a long time to develop. In some cases, symptoms can take three months to develop fully, although they can take several years.

The symptoms of ankylosing spondylitis usually start during early adulthood or in the later teenage years. The symptoms may come and go, and get better or worse over many years.

The main symptoms of ankylosing spondylitis are:

  • back pain and stiffness
  • buttock pain
  • inflammation (swelling) of the joints (arthritis)
  • painful inflammation where tendons or ligaments attach to bone (enthesitis)
  • fatigue (extreme tiredness)

If you have ankylosing spondylitis, you may not develop all of the symptoms listed above. The symptoms are explained in more detail below.

Back pain and stiffness

Back pain and stiffness are usually the main symptoms of ankylosing spondylitis. If you have ankylosing spondylitis you may find that:

  • your pain gets better with exercise but not with rest
  • your back is particularly stiff in the morning, lasting for more than 30 minutes after you start to move around
  • you wake up in the second half of the night with pain and stiffness
  • you have pain in your buttocks, which can sometimes be on one side and sometimes on the other


As well as causing symptoms in your back and spine, ankylosing spondylitis can cause arthritis in your hip, knee and other joints. The main symptoms associated with arthritis are:

  • pain on moving the joint
  • tenderness when the joint is examined
  • swelling
  • warmth in the affected area


Enthesitis is painful inflammation where a bone is joined to:

  • a tendon (a tough cord of tissue that connects muscles to bones), or
  • a ligament (a band of tissue that connects bones to bones)

Common sites for enthesitis are:

  • at the top of the shin bone
  • behind the heel
  • under the heel
  • at the ends of the ribs

If your ribs are inflamed, you will feel chest pain, and you may find it difficult to expand your chest when breathing deeply.


Fatigue is a common symptom of untreated ankylosing spondylitis. It can make you feel tired and lacking in energy.

Causes of ankylosing spondylitis

The cause of ankylosing spondylitis (AS) is not fully understood. However, a particular gene (unit of genetic material) has been identified that is closely linked to the condition.


Research has shown that most people who have ankylosing spondylitis carry a particular gene known as human leukocyte antigen B27 (HLA-B27). Among people with ankylosing spondylitis, 9 out of 10 have HLA-B27.

It is thought that having HLA-B27 may make having ankylosing spondylitis more likely. However, if you have the gene it does not necessarily mean that you will also have the condition. It is estimated that 8 in 100 people in the general population have the HLA-B27 gene but do not have ankylosing spondylitis.

Testing for the gene is not a very reliable method of diagnosing ankylosing spondylitis because some people can have the HLA-B27 gene but not have ankylosing spondylitis, and there are different subtypes of HLA-B27.

Family history

Ankylosing spondylitis can run in families, and the HLA-B27 gene can be inherited (passed on) from another family member.

If you have a close relative who has ankylosing spondylitis, such as a parent or a sibling (brother or sister), you are three times more likely to develop the condition compared with someone who does not have a relative with the condition.

Diagnosing ankylosing spondylitis

You should see your GP if you think you may have ankylosing spondylitis (AS). There is no single test to diagnose the condition, but your GP will ask you about your symptoms.

The back pain that is associated with ankylosing spondylitis is quite distinctive. For example, it usually gets worse with rest and may wake you up during the second half of the night.

Blood tests

If your GP thinks you could have ankylosing spondylitis, they may perform some blood tests, including:

  • a full blood count (FBC), which measures all of the different types of blood cells in the sample, and can help to determine whether there are fewer red blood cells (cells that transport oxygen), which may indicate anaemia
  • erythrocyte sedimentation rate (ESR) – a sample of blood is put into a test tube and the length of time that the red blood cells take to sink to the bottom of the tube is measured
  • C-reactive protein (CRP) – a blood sample is measured to see how much CRP (a protein that is produced by the liver) it contains

The ESR and CRP tests provide a measure of how much inflammation (swelling) is in your body. Inflammation in your spine and joints is one of the main symptoms of ankylosing spondylitis.

If your GP thinks you may have ankylosing spondylitis, they will refer you to a rheumatologist for further tests. A rheumatologist specialises in conditions that affect the muscles and joints.

Further tests

Your rheumatologist will carry out some imaging tests to examine the appearance of your spine and pelvis. Some possible tests are described below.


An X-ray uses short bursts of high-energy radiation to create images of hard substances in your body, such as bones. X-rays of your lower back can show severe signs of ankylosing spondylitis, such as:

  • damage to the joints at the base of your spine (the sacroiliac joints)
  • new bone forming between the vertebrae (bones) in your spine

MRI scan

A magnetic resonance imaging (MRI) scan creates an image of the inside of your body using a strong magnetic field and radio waves.

A MRI scan may highlight changes in your sacroiliac joints (at the base of your spine) that might not show up on an X-ray.

Ultrasound scan

An ultrasound scan uses sound waves to examine the inside of your body, in the same way they are used to view a baby inside the womb (uterus).

An ultrasound scan can pick up inflammation of the tissues (tendons and ligaments) that are attached to your bones.

Confirming ankylosing spondylitis

The imaging procedures described above can be used to highlight the extent of any spinal inflammation and ankylosis (fusing of the spine) that you may have.

However, as ankylosing spondylitis often takes a long time to develop, any damage to your spine may not yet be visible. This is why the condition is often difficult to diagnose. In many cases, confirming a diagnosis is a long process that can often take several years.

The criteria used to confirm the diagnosis are described below.


A definite diagnosis of ankylosing spondylitis can be confirmed if sacroiliitis (inflammation of the sacroiliac joints) is apparent on an X-ray, and you have one of the following:

  • at least three months of lower back pain that gets better with exercise and worse with rest
  • limited movement in your lumbar spine (lower back)
  • limited chest expansion compared to what is expected for your age and sex

If you have all three of these features but do not have sacroiliitis, or if you only have sacroiliitis, you will be diagnosed with ‘probable ankylosing spondylitis’.
Increasingly, MRI scans are being used to detect ankylosing spondylitis early.

Treating ankylosing spondylitis

There is no cure for ankylosing spondylitis (AS), but treatment is available. It aims to:

  • relieve your symptoms
  • prevent your symptoms from interfering with your daily life
  • slow the process of stiffening of your spine

Ankylosing spondylitis is a chronic (long-term) condition, but most people who are affected by it are fully independent and lead relatively normal lives.

If your GP thinks you have ankylosing spondylitis, they may prescribe medicines to control your symptoms. You will probably be referred to a rheumatologist (a specialist in conditions that affect the bones, muscles and joints).

The rheumatologist will advise you and your GP about continuing your treatment using:

  • physical treatments, such as physiotherapy (where physical methods, such as exercise and manipulation, are used to improve your symptoms and wellbeing)
  • medication to control the pain and relieve the symptoms

These treatments are described in more detail below.


Physical activity and exercise are very important for effectively treating ankylosing spondylitis effectively. Keeping active can improve your posture and your range of spinal movement, as well as preventing your spine from becoming stiff and painful.

As well as keeping active, physiotherapy is a key part of treating ankylosing spondylitis. Your rheumatologist will be able to refer you to a physiotherapist (a healthcare professional who is trained in using physical methods of treatment). They can advise you about the best ways to exercise. They can also draw up an exercise programme that is suitable for you.

If you have ankylosing spondylitis, the type of physiotherapy that may be recommended may include:

  • a group exercise programme, where you exercise with other people
  • an individual exercise programme – you are given exercises to do by yourself
  • massage – your muscles and other soft tissues are manipulated to relieve pain and improve movement
  • hydrotherapy – you exercise in water (usually a warm, shallow swimming pool or a special hydrotherapy bath); the weight of the water helps to improve your circulation (blood flow), relieve pain and relax your muscles
  • electrotherapy – electric currents or impulses (small electric shocks) make your muscles contract (tighten), which can help ease pain and promote healing

Some people prefer to swim or play sport to keep flexible. This is usually fine, although some daily stretching and exercise is also important (see below).

See about Physiotherapy for more information about the wide range of different techniques that can be used.


The National Ankylosing Spondylitis Society (NASS) provides detailed information about different types of exercise that may help you to effectively manage your condition.

However, if you are in doubt, get advice from your physiotherapist or rheumatologist before taking up a new form of exercise or sport.

Alongside physiotherapy, you will also probably be prescribed medication. The different types of medications that you may be prescribed include:

  • painkillers
  • tumour necrosis factor (TNF) blockers
  • bisphosphonates
  • disease-modifying anti-rheumatic drugs (DMARDs)
  • corticosteroids

These are described below.


Your GP may prescribe painkillers to manage your condition while you are being referred to a rheumatologist. The rheumatologist may continue prescribing painkillers, although not everyone needs them, at least not all the time. The first type of painkiller that is usually prescribed is a non-steroidal anti-inflammatory drug (NSAID).

Non-steroidal anti-inflammatory drugs (NSAIDs)

As well as helping to ease pain, non-steroidal anti-inflammatory drugs (NSAIDs) will also help to relieve inflammation (swelling) in your joints. Therefore, they are usually an effective treatment for ankylosing spondylitis. Examples of NSAIDs include:

  • ibuprofen
  • naproxen
  • diclofenac

When prescribing NSAIDs, your GP or rheumatologist will try to find the one that suits you best and the lowest possible dose that relieves your symptoms. Your dose will be monitored and reviewed as necessary.


NSAIDs may be unsuitable for you if you:

  • have asthma – a condition that causes the airways of the lungs (the bronchi) to become inflamed
  • have high blood pressure (hypertension)
  • have kidney or heart problems
  • have, or have previously had, stomach problems, such as a peptic ulcer
  • are pregnant
  • are also taking other medications, such as aspirin or warfarin (medicine to stop your blood clotting)


If NSAIDs are unsuitable for you, an alternative painkiller, such as paracetamol, may be recommended.

Paracetamol rarely causes side effects and can be used in women who are pregnant or breastfeeding. However, paracetamol may not be suitable for people with liver problems or those who are dependent on alcohol (have an alcohol addiction).


If necessary, as well as paracetamol, you may also be prescribed a stronger type of painkiller called codeine. Codeine can cause side effects including:

  • nausea (feeling sick)
  • vomiting (being sick)
  • constipation (an inability to empty your bowels)
  • drowsiness, which could affect your ability to drive

Tumour necrosis factor (TNF) blocker

If your symptoms of ankylosing spondylitis cannot be controlled using painkillers or exercising and stretching, a tumour necrosis factor (TNF) blocker may be recommended for you. TNF is a chemical that is produced by cells when tissue is inflamed.

TNF blockers are given by injection and work by preventing the effects of TNF. This helps reduce the inflammation in your joints that is caused by ankylosing spondylitis. Examples of TNF blockers include:

  • adalimumab
  • etanercept

Side effects

Side effects from adalimumab and etanercept include:

  • reactions at the site of the injection, such as redness or swelling
  • infections, which can be severe, such as tuberculosis (an infection of the lungs) or septicaemia (blood poisoning)
  • nausea (feeling sick)
  • abdominal (tummy) pain
  • headache

See the patient information leaflet that comes with your medication for a full list of side effects.

TNF alpha blockers are a relatively new form of treatment for ankylosing spondylitis, and their long-term effects are unknown. However, research into the use of TNF blockers for treating rheumatoid arthritis (a type of arthritis that makes your joints feel stiff and can leave you feeling tired and unwell) is providing clearer information about their long-term safety.

If your rheumatologist recommends using TNF blockers, the decision about whether they are right for you must be discussed carefully, and your progress will be closely monitored. The main reason for this is that TNF blockers interfere with the immune system (the body’s natural defence system).

NICE guidelines

The National Institute for Health and Clinical Excellence (NICE) has produced guidance about the use of these TNF blockers. NICE states that adalimumab and etanercept may only be used if:

  • your diagnosis of ankylosing spondylitis has been confirmed (see Ankylosing spondylitis – diagnosis)
  • your level of pain is assessed twice (using a simple scale that you fill in) 12 weeks apart and confirms that your condition is still active (has not improved)
  • your Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) is tested twice, 12 weeks apart, and confirms that your condition is still active (BASDAI is a set of measures devised by experts to evaluate your condition by asking a number of questions about your symptoms)
  • treatment with two or more NSAIDs for four weeks at the highest possible dose has not controlled your symptoms

After 12 weeks of treatment with adalimumab or etanercept, your pain score and BASDAI will be tested again to see whether or not they have improved sufficiently to make continued treatment worthwhile for you. If they have, treatment with adalimumab or etanercept will continue and you will be tested every 12 weeks.

If there is not enough improvement after 12 weeks, you will be tested again after six weeks. If treatment with adalimumab or etanercept is still not effective, the treatment will be stopped.

If you cannot understand the BASDAI and pain tests, for example, because of a learning difficulty or because they are not available in a language you easily understand, it will be possible to assess the appropriateness and effects of TNF blocker drugs in other ways (an alternative method of assessment may be used).

Infliximab is an alternative TNF blocker that may be used to treat ankylosing spondylitis. However, it is not recommended by NICE. If you are currently taking infliximab, you should continue to do so until you and your rheumatologist decide that it is appropriate for you to stop.

Other new TNF blockers and similar medications are being developed and may be approved by NICE.


Bisphosphonates are usually used to treat osteoporosis (weak and brittle bones), which can sometimes develop as a complication of ankylosing spondylitis. Bisphosphonates may also be effective in treating ankylosing spondylitis, although the evidence is not entirely clear. They may be used if you also have osteoporosis.

Bisphosphonates can be taken by mouth (orally) as tablets or given by injection.

Disease-modifying anti-rheumatic drugs (DMARDs)

Disease-modifying anti-rheumatic drugs (DMARDs) are an alternative type of medication that is often used to treat other types of arthritis, such as rheumatoid arthritis. DMARDs may be prescribed for ankylosing spondylitis, although they are only beneficial if other joints are involved rather than the spine.

Two DMARDs have been studied for possible benefits in people with ankylosing spondylitis. Both may be helpful for inflammation of joints other than the spine, although neither seems to be helpful for spinal symptoms. They are:

  • sulfasalazine
  • methotrexate

Both are known to be effective for treating rheumatoid arthritis, but there is not currently enough evidence of the benefits of methotrexate for ankylosing spondylitis.


Sulfasalazine can cause a number of side effects, such as:

  • nausea
  • vomiting
  • heartburn (when stomach acid leaks back up into your gullet)
  • serious skin reactions


Corticosteroid medicines (steroids) have a powerful anti-inflammatory effect and can be taken in various ways, for example as:

  • tablets (oral)
  • injections (parenteral)

If a particular joint is inflamed, corticosteroids can possibly be injected directly into the joint. Corticosteroids are sometimes used to treat other types of arthritis because they can reduce the pain, stiffness and swelling in a joint.

After the injection you will need to rest the joint for up to 48 hours (two days). It is usually considered wise to have a corticosteroid injection up to three times in one year, with at least three months between injections in the same joint. This is because corticosteroids injections can cause a number of side effects, such as:

  • inflammation in response to the injection
  • the skin around the injection may change colour (depigmentation)
  • the surrounding tissue may waste away
  • a tendon (cord of tissue that connects muscles to bones) near the joint may rupture (burst)

Corticosteroids may also help to calm down painful swollen joints when taken as tablets. Occasionally, when pain and stiffness are severe, corticosteroids can be very helpful when given as an injection into your muscle (intramuscular injection).

Complications of ankylosing spondylitis

Ankylosing spondylitis (AS) is a complex condition that can affect many parts of your body. It can cause complications in your day-to-day life, and lead to additional health conditions.

Some of the complications associated with ankylosing spondylitis are briefly outlined below.


Uveitis, also known as iritis, is a condition that is sometimes associated with ankylosing spondylitis. Uveitis is inflammation (redness and swelling) of part of the eye. It usually only affects one eye, not both. If you have uveitis, your eye will become:

  • red
  • painful
  • sensitive to light (photophobia)

Because uveitis can damage your eyesight, if you have ankylosing spondylitis and you develop pain or redness in one eye, or misty vision, you should urgently visit:

  • your GP
  • an ophthalmologist (a medical doctor who specialises in eye disease and its treatment or surgery), or
  • an optometrist (a person who examines eyes and tests sight)

Uveitis is easily treated using eye drops. If treated quickly, uveitis usually clears up within two to three weeks. However, if uveitis is not treated quickly, it can cause the loss of some or all of your vision.


Osteoporosis is a condition that causes your bones to become weak and brittle. In ankylosing spondylitis, osteoporosis can develop in the spine.

Spinal fractures

Having ankylosing spondylitis increases your risk of developing fractures (breaks) in the vertebrae of your spine. This risk increases with the duration of your condition.

Cardiovascular disease

If you have ankylosing spondylitis, your risk of developing a cardiovascular disease (condition that affects the heart and blood flow), such as a heart attack or stroke, is slightly higher than someone who does not have the condition.

Due to the increased risk, it is important to take steps to minimise your chances of developing cardiovascular disease. Your rheumatologist will be able to advise you about lifestyle changes. You can also refer to Ankylosing spondylitis – self help for more information.

Reduced flexibility

It is estimated that 4 in 10 people with ankylosing spondylitis will eventually have severely restricted spinal flexibility. Spinal deformities are likely to take at least 10 years to develop.

Fixed posture

In very severe cases of ankylosing spondylitis, the pain and stiffness in your lower back can also spread to the upper parts of your spine. This can decrease the mobility of your spine, making it difficult to move. As a result, your posture can become fixed in one position. This may:

  • make it difficult to look people in the eye
  • reduce your self-confidence

However, it is unlikely that this will cause severe disability unless you also have severe arthritis (inflammation of the joint and bones) in your hips.

Surgical treatment

Two types of surgical treatment are sometimes needed by people with ankylosing spondylitis:

  • joint replacement surgery
  • spinal corrective surgery

These are described in more detail below.

Joint replacement surgery

In some cases, it may be necessary to have surgery to replace a joint that has become severely damaged as a result of ankylosing spondylitis. For example, if the hip joints are affected, a hip replacement may help to:

  • relieve pain
  • improve mobility

Spinal corrective surgery

It is now rare for people with ankylosing spondylitis to need their spine straightened, but if the spine becomes badly bent this can often be corrected by an operation.

Cauda equina syndrome

Cauda equina syndrome is a very rare complication of ankylosing spondylitis that occurs when the nerves at the bottom of your spine become compressed (compacted).

Cauda equina syndrome causes:

  • pain or numbness in your lower back and buttocks
  • weakness in your legs, which can affect your ability to walk
  • urinary incontinence or bowel incontinence (when you cannot control your bladder or bowels)

See your GP as soon as possible if you have ankylosing spondylitis and you develop any of these symptoms.


In very rare cases, it is possible to develop amyloidosis as a complication of ankylosing spondylitis.

Amyloid is a protein that is produced by cells in your bone marrow (the spongy material that is found in the centres of some hollow bones). Amyloidosis is a condition where amyloid builds up in organs, such as your:

  • heart – a muscular organ that pumps blood around the body
  • kidneys – two bean-shaped organs that filter out waste products from the blood
  • liver – the largest organ in the body; it performs many important functions, such as turning food into energy

The symptoms of amylodosis vary because the condition can affect many different areas of your body. In some cases, there may be no symptoms at all.


As ankylosing spondylitis advances, it can affect your ability to work. It is estimated that a third of people with ankylosing spondylitis may be unable to work at all. Around one in six people may need to make changes to their working life in order to continue working, such as:

  • working part-time
  • working from home
  • not taking up physically demanding occupations

When at work, it is important to maintain a good posture when sitting or standing for long periods of time. You should get up, stretch and move around regularly. This could mean adjusting your work station, or ensuring that you take regular breaks.

Self-care advice

If you have been diagnosed with ankylosing spondylitis, the self care advice that is outlined below may prove useful.

  • Make sure that you take the medicines that have been prescribed for you.
  • Make sure you do the stretches and exercises that your physiotherapist (a healthcare professional who is trained in using physical methods of treatment) recommends for you.
  • Make sure that you maintain a good posture when you are sitting and sleeping (see the video, left).
  • Do not smoke. As well as having a negative impact on your overall health, smoking is particularly risky for people with ankylosing spondylitis as it increases your risk of developing cardiovascular disease (conditions that affect the heart and blood flow, such as heart attacks).
  • Using hot or cold packs may help to relieve back and joint pain.

Lifestyle changes

If you have ankylosing spondylitis, you may also have an increased risk of developing cardiovascular disease. Cardiovascular diseases include:

  • heart disease – your heart’s blood supply is blocked or interrupted by a build-up of fatty substances in the coronary arteries (the blood vessels that supply blood to the heart)
  • stroke – a serious medical condition that occurs when the blood supply to the brain is interrupted
  • deep vein thrombosis (DVT) – where blood clots develop in one of the deep veins in your body, usually in your legs

Your rheumatologist (specialist in treating muscle and joint conditions) will be able to advise you about any lifestyle changes you should make to minimise your risk of developing a cardiovascular disease. These changes may include:

  • giving up smoking (if you smoke)
  • losing weight (if you are overweight or obese)
  • taking more regular exercise
  • keeping any other conditions that you may have under control, such as diabetes (a long-term condition caused by too much glucose in the blood) or high blood pressure (hypertension)