In ankylosing spondylitis (AS), several parts of the lower spine become inflamed, including the vertebrae (bones in the spine) and spinal joints.

Over time, this can damage the spine and lead to the growth of new bone, which in some cases can cause parts of the spine to join up (fuse) and lose flexibility. This is known as ankylosis.

It is not known exactly what causes AS, but in many cases there seems to be a link with a particular gene known as HLA-B27.

HLA-B27 gene

Research has shown that more than 9 out of 10 people with AS carry a particular gene known as human leukocyte antigen B27 (HLA-B27).

Having this gene does not necessarily mean you will develop AS. It is estimated that 8 in every 100 people in the general population have the HLA-B27 gene, but most do not have AS.

It is thought that having this gene may make you more vulnerable to developing AS, and the condition is triggered by one or more environmental factors – although it is not known what these are.

Testing for this gene may be carried out if AS is suspected. However, this test is not a very reliable method of diagnosing the condition because some people can have the HLA-B27 gene but not have ankylosing spondylitis.

Read about how ankylosing spondylitis is diagnosed.

Can ankylosing spondylitis be inherited?

AS can run in families, and the HLA-B27 gene can be inherited from another family member.

If you have AS and tests have shown you carry the HLA-B27 gene, the chance of any children you have developing the condition is less than 20%. If you have AS but don’t carry the HLA-B27 gene, the chance of any children you have developing the condition is less than 10%.

If you have a close relative who has AS, 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.

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 complications associated with AS are outlined below.

Reduced flexibility

Although most people with AS remain fully independent or minimally disabled in the long term, around 4 in every 10 people with the condition will eventually have severely restricted movement in their spine.

This usually only affects the lower back and is the result of the bones in the spine fusing (joining up).

Fusing of the spine can make it difficult to move your back and can mean your posture becomes fixed in one position, although it doesn’t lead to severe disability in most cases.

In rare cases, surgery may be recommended to correct severe bends in the spine.

Joint damage

AS can cause joints such as the hips and knees to become inflamed. This can damage the affected joints over time, making them painful and difficult to move.

If a joint becomes particularly damaged, you may need surgery to replace it with an artificial one.

Iritis

Iritis, also known as anterior uveitis, is a condition sometimes associated with AS where the front part of the eye becomes red and swollen. It usually only affects one eye, rather than both.

If you have iritis, your eye may become red, painful and sensitive to light (photophobia). Your vision may also become blurred or cloudy.

You should visit your GP as soon as possible if you have AS and think you may have developed iritis, as the condition can cause the loss of some or all of your vision if not treated promptly.

If your GP thinks you have iritis, they will refer you urgently to an ophthalmologist (a medical doctor who specialises in eye problems) for treatment.

Iritis can usually be treated with corticosteroid eye drops.

Osteoporosis and spinal fractures

Osteoporosis is where the bones become weak and brittle. In AS, osteoporosis can develop in the spine and can increase your risk of fracturing the bones in your backbone. The longer you have the condition, the more this risk increases.

If you do develop osteoporosis, you will usually need to take medication to help strengthen your bones. There are a number of medications that can be used to treat osteoporosis, which can be taken by mouth (orally) as tablets or given by injection.

Read more about treating osteoporosis.

Cardiovascular disease

If you have AS, you may also have an increased risk of developing cardiovascular disease (CVD). CVD is a general term that describes a disease of the heart or blood vessels, such as heart disease and stroke.

Due to this increased risk, it is important to take steps to minimise your chances of developing CVD.

Your rheumatologist (a specialist in treating muscle and joint conditions) can advise about lifestyle changes you should make to minimise your risk of developing a CVD. These changes may include:

• stopping smoking – if you smoke
• losing weight – if you are overweight or obese
• taking regular exercise – 150 minutes of exercise per week can greatly increase your health
• making changes to your diet to keep other conditions you may have under control – such as diabetes or high blood pressure

You may also be prescribed medication to reduce your blood pressure or blood cholesterol level.

Cauda equina syndrome

Cauda equina syndrome is a very rare complication of AS that occurs when 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 AS and you develop any of these symptoms.

Amyloidosis

In very rare cases, it is possible to develop a condition called amyloidosis as a complication of AS.

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

Amyloidosis can cause a wide range of symptoms, including fatigue, weight loss, fluid retention (oedema), shortness of breath and numbness or tingling in the hands and feet.

Problems with employment

Over time, AS can increasingly affect your ability to work. Some people with the condition may be unable to work at all and others may need changes to their working life, such as working part-time, working from home or avoiding physically demanding work.

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 you take regular breaks. Read more about how to sit correctly.

The National Ankylosing Spondylitis Society (NASS) has more information on living with Ankylosing Spondylitis, including advice about the condition and employment.

Ankylosing spondylitis (AS) can be difficult to diagnose because the condition develops slowly and there is no definitive test to confirm a diagnosis.

The first thing you should do if you think you have AS is to see your GP. They will ask about your symptoms, including what symptoms you are experiencing, when they started and how long you have had them.

Back pain associated with AS can be quite distinctive. For example, it usually doesn’t improve with rest and may wake you up during the night.

Blood tests

If your GP suspects AS, they may arrange blood tests to check for signs of inflammation in your body. Inflammation in your spine and joints is one of the main symptoms of the condition.

If your results suggest you do have inflammation, you will be referred to a rheumatologist for further tests. A rheumatologist is a specialist in conditions that affect muscles and joints.

Further tests

Your rheumatologist will carry out imaging tests to examine the appearance of your spine and pelvis, as well as further blood tests. These are described below.

X-rays

An X-ray of your lower back can show damage to the joints at the base of your spine (the sacroiliac joints) and new bone forming between the vertebrae (bones in your spine), which are common signs of advanced AS.

MRI scan

A magnetic resonance imaging (MRI) scan may highlight changes in your sacroiliac joints that might not show up on an X-ray. It may also show any inflammation of ligaments in the spinal region.

Ultrasound scan

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

Genetic testing

A genetic blood test may sometimes be carried out to see if you carry the HLA-B27 gene, which is found in most people with AS.

This can contribute towards a diagnosis of AS, but it is not entirely reliable as not everyone with the condition has this gene, and some people have the gene without ever developing AS.

Confirming ankylosing spondylitis

Although scans can sometimes show spinal inflammation and fusing of the spine (ankylosis), damage to the spine cannot always be picked up in the early stages of AS.

This is why diagnosis is often difficult. In many cases, confirming a diagnosis is a long process that can take years.

A diagnosis of AS can usually be confirmed if an X-ray shows sacroiliitis (inflammation of the sacroiliac joints) and you have at least one of the following:

• at least three months of lower back pain that gets better with exercise and doesn’t improve 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”.

Ankylosing spondylitis (AS) is a long-term (chronic) condition in which the spine and other areas of the body become inflamed.

The symptoms of AS can vary but usually involve:

• back pain and stiffness that improves with exercise and isn’t relieved by rest
• pain and swelling in other parts of the body, such as the hips, knees and ribs
• fatigue (extreme tiredness)

These symptoms tend to develop gradually, usually over several months or years, and may come and go over time.

In some people, the condition gets better with time, but for others it can get slowly worse.

Read more about the symptoms of ankylosing spondylitis 

When to seek medical advice

You should see your GP if you have persistent symptoms of AS.

If your GP thinks you may have the condition, they should refer you to a rheumatologist (a specialist in conditions affecting muscles and joints) for further tests and any necessary treatment.

Read more about diagnosing ankylosing spondylitis.

What causes ankylosing spondylitis?

In AS, various areas of the spine and other joints become inflamed.

As well as causing pain, stiffness and swelling, this inflammation can damage affected areas of the body over time, and in some cases can lead to some of the individual bones of the spine fusing (joining together). This fusing of the spine is known as ankylosis.

It is not known what causes the condition, but there is thought to be a link with a particular gene known as HLA-B27.

Read more about the causes of ankylosing spondylitis.

Who is affected

AS tends to first develop in teenagers and young adults. Most cases first start in people aged 20-30, with only a minority of cases first affecting adults over 45.

AS is around three times more common in men than in women.

There are around 200,000 people in the UK who have been diagnosed with the condition.

How ankylosing spondylitis is treated

There is no cure for AS and it is not possible to reverse the damage caused by the condition. However, treatment is available to relieve the symptoms and help prevent or delay its progression.

In most cases, treatment will involve a combination of:

• exercises carried out individually or in groups to reduce pain and stiffness
• physiotherapy – where physical methods, such as massage and manipulation, are used to improve comfort and spinal flexibility
• medication to help relieve pain and reduce inflammation – such as painkillers and a type of medicine called anti-TNF medication

Surgery is sometimes needed to repair significantly damaged joints or correct severe bends in the spine, but this is uncommon.

Read more about treating ankylosing spondylitis.

Outlook

The outlook for AS is highly variable. For some people, the condition improves after an initial period of inflammation, whereas for others the condition can get progressively worse over time.

Around 70-90% of people with AS remain fully independent or minimally disabled in the long term. However, some people eventually become severely disabled due to the bones in their spine fusing in a fixed position and damage to other joints, such as the hips or knees.

With modern treatments, AS doesn’t normally affect life expectancy significantly, although the condition is associated with an increased risk of other potentially life-threatening problems.

For example, AS can lead to osteoporosis (weakening of the bones), spinal fractures and cardiovascular disease (a group of conditions affecting the heart and blood vessels).

Read more about the complications of ankylosing spondylitis.

The symptoms of ankylosing spondylitis (AS) can vary from person to person, but usually develop slowly, over several months or years.

AS usually first starts to develop during later teenage years or early adulthood. The symptoms may come and go, and improve or get worse over many years.

Main symptoms

The main symptoms of AS are described below, although you may not develop all of these if you have the condition. 

Back pain and stiffness

Back pain and stiffness are usually the main symptoms of AS. You may find:

• the pain gets better with exercise but doesn’t improve, or gets worse, with rest
• the pain and stiffness is worse in the morning and at night – you may wake up regularly during the night because of the pain
• you have pain in the area around your buttocks

Arthritis

As well as causing symptoms in your back and spine, AS can also cause inflammation of the joints (arthritis) in other parts of your body, such as your hips and knees. The main symptoms associated with arthritis are:

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

Enthesitis

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 (Achilles tendon)
• under the heel
• where the ribs join to the breast bone

If your ribs are affected, you may experience chest pain, and you may find it difficult to expand your chest when breathing deeply.

Fatigue

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

When to seek medical advice

You should see your GP if you have persistent symptoms of AS.

If your GP thinks you may have the condition, they should refer you to a rheumatologist (a specialist in conditions affecting muscles and joints) for further tests and any necessary treatment.

Read more about diagnosing ankylosing spondylitis.

There is no cure for ankylosing spondylitis (AS), but treatment is available to help relieve the symptoms.

Treatment can also help delay or prevent the process of the spine fusing (joining up) and stiffening.

In most cases, treatment will involve a combination of exercise, physiotherapy and medication, which are described below.

There is a summary of the pros and cons of the available treatments, so you can compare your options.

Physiotherapy and exercise

Keeping active can improve your posture and range of spinal movement, along with preventing your spine from becoming stiff and painful.

As well as keeping active, physiotherapy is a key part of treating AS. A physiotherapist (a healthcare professional trained in using physical methods of treatment) can advise about the most effective exercises and draw up an exercise programme that suits you.

Types of physiotherapy recommended for AS include:

• a group exercise programme – where you exercise with others
• 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 (the bones of the spine should never be manipulated as this can cause injury in people with AS)
• hydrotherapy – exercise in water (usually a warm, shallow swimming pool or a special hydrotherapy bath); the buoyancy of the water helps make movement easier by supporting you, and the warmth can relax your muscles 

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

If you’re ever in doubt, speak to your physiotherapist or rheumatologist before taking up a new form of sport or exercise.

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

Painkillers

You may need painkillers to manage your condition while you are being referred to a rheumatologist. The rheumatologist may continue prescribing painkillers, although not everyone needs them all the time.

Non-steroidal anti-inflammatory drugs (NSAIDs)

The first type of painkiller usually prescribed is a non-steroidal anti-inflammatory drug (NSAID). As well as helping to ease pain, NSAIDs can help relieve swelling (inflammation) in your joints.

Examples of NSAIDs include ibuprofen, naproxen and diclofenac.

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

Paracetamol

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 dependent on alcohol.

Codeine

If necessary, as well as paracetamol, you may also be prescribed a stronger type of painkiller called codeine.

Codeine can cause side effects including feeling sick, vomiting, constipation and drowsiness.

Anti-TNF medication

If your symptoms cannot be controlled using painkillers or exercising and stretching, anti-TNF (tumour necrosis factor) medication may be recommended. TNF is a chemical produced by cells when tissue is inflamed.

Anti-TNF medications are given by injection and work by preventing the effects of TNF, as well as reducing inflammation in your joints caused by ankylosing spondylitis.

Examples of anti-TNF medication include adalimumab, etanercept and golimumab.

These are relatively new treatments for AS, and their long-term effects are unknown.

However, they have been used for longer in people with rheumatoid arthritis, and this is providing clearer information about their long-term safety.

If your rheumatologist recommends using anti-TNF medication, the decision about whether they are right for you must be discussed carefully and your progress will be closely monitored. This is because anti-TNF medication can interfere with the immune system (the body’s natural defence system), increasing your risk of developing potentially serious infections.

NICE guidelines

The National Institute for Health and Care Excellence (NICE) has produced guidance about the use of anti-TNF medication for AS. NICE states that adalimumab, etanercept and golimumab may only be used if:

• your diagnosis of ankylosing spondylitis has been confirmed
• your level of pain is assessed twice (using a simple scale that you fill in) 12 weeks apart and confirms your condition has not improved
• your Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) is tested twice, 12 weeks apart, and confirms your condition has not improved – 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 anti-TNF medication, your pain score and BASDAI will be tested again to see whether they have improved enough to make continuing treatment worthwhile. If they have, treatment will continue and you will be tested every 12 weeks.

If there is not enough improvement after 12 weeks, you will be tested again at a later date or the treatment will be stopped.

Corticosteroids

Corticosteroids have a powerful anti-inflammatory effect and can be taken as tablets or injections by people with AS.

If a particular joint is inflamed, corticosteroids can be injected directly into the joint. After the injection, you will need to rest the joint for up to 48 hours.

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:

• infection 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 calm down painful swollen joints when taken as tablets.

Disease-modifying anti-rheumatic drugs (DMARDs)

Disease-modifying anti-rheumatic drugs (DMARDs) are an alternative type of medication often used to treat other types of arthritis.

DMARDs may be prescribed for AS, although they are only beneficial in treating pain and inflammation in joints in areas of the body other than the spine.

Two DMARDs sometimes used to treat inflammation of joints other than the spine include sulfasalazine and methotrexate.

Surgery

Most people with AS will not need surgery.

However, in cases where a joint has become severely damaged, joint replacement surgery may be recommended to improve pain and movement in the affect joint. For example, if the hip joints are affected, a hip replacement may be carried out.

In rare cases, corrective surgery may be needed if the spine becomes badly bent.

Follow-up

As the symptoms of AS develop slowly and tend to come and go, you will need to see your rheumatologist or GP for regular check-ups.

They will make sure your treatment is working properly and may carry out physical assessments to assess how your condition is progressing. This may involve further sets of the same blood tests or X-rays you had at the time of your diagnosis.

Any complications of ankylosing spondylitis that arise will be treated as they develop.