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.


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.

Information about you

If you have AS, your clinical team will pass information about you on to the National Congenital Anomaly and Rare Diseases Registration Service (NCARDRS).

This helps scientists look for better ways to prevent and treat this condition. You can opt out of the register at any time.

Find out more about the register.

Ankylosing spondylitis (AS)

Ankylosing spondylitis is a type of arthritis that affects parts of the spine. In this video, an expert describes the long-term effects of the condition, its most common symptoms and the different treatments available.

Media last reviewed: 12/05/2016

Next review due: 12/05/2018

The spine

Your spine extends from your skull to your pelvis. It is made up of 24 individual bones called vertebrae, which are stacked on top of each other.

The vertebrae are separated by soft pads, or discs, that act as shock absorbers. Each vertebra has two sets of joints called facet joints that, with the discs, allow the spine to bend.

The vertebrae are also held together by tough bands called ligaments. Together with the spinal muscles, the ligaments give the back its strength.

At the bottom of the back there are the two sacroiliac joints at either side of the spine. These transmit the weight of the upper body to the pelvis.

Page last reviewed: 26/06/2014

Next review due: 26/06/2016