The symptoms of ankylosing spondylitis (AS) usually develop slowly over several months or years. The symptoms may come and go, and improve or get worse, over many years.

AS usually first starts to develop between 20 to 30 years of age.

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 does not 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 the breast bone

If your ribs are affected, you may experience chest pain and 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.

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

Over time this can damage the spine and lead to the growth of new bone. In some cases this can cause parts of the spine to join up (fuse) and lose flexibility (ankylosis).

It's 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 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'll develop AS. It's estimated 8 in every 100 people in the general population have the HLA-B27 gene, but most do not have AS.

It's thought having this gene may make you more vulnerable to developing AS. The condition may be triggered by 1 or more environmental factors, although it's 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 show you carry the HLA-B27 gene then there is a 1 in 2 chance that you could pass on the gene to any children you have. It is estimated that between 5 to 20% of children with this gene will then go on to develop AS.

Ankylosing spondylitis (AS) can be difficult to diagnose because the condition develops slowly and there's no definitive test.

The first thing you should do if you think you have AS is to see your GP. They'll ask about your symptoms, including:

• what symptoms you're experiencing
• when they started
• how long you've had them

Back pain associated with AS can be quite distinctive. For example, it usually does not 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 a main symptom of the condition.

If your results suggest you do have inflammation, you'll 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 may include:

• an X-ray
• a MRI scan
• an ultrasound scan

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's 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 inflammation of the sacroiliac joints (sacroiliitis) and you have at least 1 of the following:

• at least 3 months of lower back pain that gets better with exercise and doesn't improve with rest
• limited movement in your lower back (lumbar spine)
• limited chest expansion compared with what is expected for your age and sex

If you have all 3 of these features but do not have sacroiliitis – or if you only have sacroiliitis – you'll be diagnosed with probable ankylosing spondylitis.

There's 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 joining up (fusing) and stiffening.

In most cases treatment involves a combination of:

• exercise
• physiotherapy
• medicine

Physiotherapy and exercise

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

As well as keeping active, physiotherapy is a key part of treating AS. A physiotherapist 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're 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 ease pain, NSAIDs can help relieve swelling (inflammation) in your joints.

Examples of NSAIDs include:

• ibuprofen
• naproxen
• diclofenac
• etoricoxib

When prescribing NSAIDs, your GP or rheumatologist will try to find the 1 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, you may also be prescribed a stronger type of painkiller called codeine as well as paracetamol.

Codeine can cause side effects, including: 

• feeling sick
• being sick
• constipation
• drowsiness

Biological treatments

Anti-TNF medicine

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

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

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 medicine, the decision about whether they're right for you must be discussed carefully, and your progress will be closely monitored.

In rare cases anti-TNF medicine can interfere with the immune system, increasing your risk of developing potentially serious infections.

If your symptoms do not improve significantly after taking anti-TNF medicine for 3 months the treatment will be stopped.

Secukinumab

Secukinumab is a medicine that may be offered to people with AS who do not respond to NSAIDs or anti-TNF medicine.

Secukinumab works by blocking the effects of a protein involved in triggering inflammation.

Secukinumab is not routinely available on the NHS for people with AS so you may have to pay for it.

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. You'll need to rest the joint for up to 48 hours after the injection.

It's usually recommended to limit corticosteroid injections to no more than 3 times in one year, with at least 3 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 near the joint may burst (rupture)

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 medicine often used to treat other types of arthritis.

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

Sulfasalazine is the main DMARD sometimes used to treat inflammation of joints other than the spine.

Surgery

Most people with AS will not need surgery. However, joint replacement surgery may be recommended to improve pain and movement in the affected joint if the joint has become severely damaged.

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'll need to see your rheumatologist or GP for regular check-ups.

They'll 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.

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.

Reduced flexibility

Although most people with AS remain fully independent or minimally disabled in the long term, some people with the condition 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 joining up (fusing).

Fusing of the spine can make it difficult to move your back and can mean your posture becomes fixed in 1 position, although it does not 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 joint.

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 1 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'll refer you urgently to an ophthalmologist, a medical doctor who specialises in eye problems, for treatment.

Iritis can usually be treated with corticosteroid eyedrops.

Osteoporosis and spinal fractures

Osteoporosis is where the bones become weak and brittle. In AS osteoporosis can develop in the spine and 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'll usually need to take medicine to help strengthen your bones.

There are a number of medicines that can be used to treat osteoporosis, which can be taken by mouth (orally) as tablets or given by injection.

Read 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.

Because of this increased risk, it's 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 a week can greatly improve 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 medicine 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's 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.

It can cause a wide range of symptoms, including: 

• fatigue
• weight loss
• fluid retention (oedema)
• shortness of breath
• numbness or tingling in the hands and feet