Ankylosing Spondylitis

Persistent inflammation and stiffening of the joints, usually affecting the spine and pelvis

  • Usually begins in late adolescence or early adulthood; onset rare over the age of 45
  • About four times more common in males
  • Sometimes runs in families
  • Lifestyle is not a significant factor

In ankylosing spondylitis, persistent joint inflammation affects the sacroiliac joints at the back of the pelvis and the vertebrae (bones of the spine) in particular. If the spine is severely diseased, new bone grows between the vertebrae, which eventually fuse together.

This form of arthritis is four times more common in men than in women. A variant of ankylosing spondylitis is associated, in some cases, with the persistent skin disorder psoriasis or with inflammatory bowel disease, such as Crohn’s disease.

What are the causes?

The cause of ankylosing spondylitis is unknown, but about 9 in 10 affected people have a particular antigen (a substance that is capable of stimulating an immune response in the body) called HLA-B27 on the surface of most cells. This antigen is inherited, which helps to explain why ankylosing spondylitis runs in some families. Most people with HLA-B27 do not develop the condition, and a bacterial infection is thought to trigger ankylosing spondylitis in those who are predisposed.

What are the symptoms?

The symptoms of ankylosing spondylitis usually appear in late adolescence or early adulthood and develop gradually over a period of months or even years. Men are usually more severely affected. The main symptoms include:

  • Lower back pain, which may spread down into the buttocks and thighs.

  • Lower back stiffness that may be worse in the morning and improves with exercise.

  • Pain in other joints, such as the hips, knees, and shoulders.

  • Pain and tenderness in the heels.

  • Tiredness, weight loss, and mild fever.

If left untreated, ankylosing spondylitis can distort the spine (see Kyphosis and lordosis), resulting in a stooped posture. If the joints between the spine and the ribs are affected, expansion of the chest becomes restricted. In some people, ankylosing spondylitis causes inflammation or damage to tissues in areas other than the joints, such as the eyes (see Uveitis).

How is it diagnosed?

Your doctor may suspect that you have ankylosing spondylitis from the pattern of your symptoms. He or she will perform a physical examination and may arrange for an X-ray to look for evidence of fusion in the joints of the pelvis and the spine. Your doctor may also arrange for you to have blood tests to measure the level of inflammation and look for the HLA-B27 antigen.

What is the treatment?

Treatment of ankylosing spondylitis is aimed at relieving symptoms and preventing the development of spinal deformity. Your doctor may prescribe a nonsteroidal anti-inflammatory drug to control pain and inflammation. Occasionally, a short course of oral corticosteroids may be prescribed for the short-term relief of symptoms, and injection of a corticosteroid into a severely affected joint may sometimes be given to ease pain in the joint. In severe cases, drugs such as infliximab or adalimumab may be given. These drugs work by inhibiting a natural chemical called tumour necrosis factor-alpha that promotes inflammation.

In addition to medication, your doctor may refer you for physiotherapy, which may include breathing exercises and daily exercises to help to improve your posture, strengthen the back muscles, and prevent deformities of the spine (see Preventing back pain). You may also benefit from regular physical activity, such as swimming, which may help to relieve pain and stiffness. If a joint such as a hip is affected, you may eventually need to have it replaced surgically (see Joint replacement). If your mobility is severely reduced, you may need occupational therapy. The therapist may suggest that you use specially designed equipment and furniture to make your life easier.

What is the prognosis?

Although the condition is not curable, most people with ankylosing spondylitis are only mildly affected, causing minimum disruption of their everyday lives. In many cases, early treatment and regular exercise help to relieve pain and stiffness of the back and prevent deformity of the spine. However, about 1 in 20 people who develop ankylosing spondylitis may eventually become disabled and have difficulty in carrying out many routine activities. If disability is due to an affected joint, a replacement may be carried out.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

Back to top