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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.

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.

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, 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 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.

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:

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

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.

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: