Ankylosing Spondylitis

What is ankylosing spondylitis?

Ankylosing spondylitis (AS) is an autoimmune disease that affects the spine.

In autoimmune disease the immune system does not work as it should. Normally, the immune system protects the body from infection, but in autoimmune disease it attacks the body instead.

In AS it attacks the spine, causing pain and inflammation. It may also affect other parts of the body, including hips, knees and ribs.

Who is affected by ankylosing spondylitis?

The exact number of people with AS is unknown, but it affects around 0.2% of the population of Europe and 0.3% of North America. It usually occurs between 20 and 30 years of age, and rarely after the age of 45 years.1

What are the symptoms of ankylosing spondylitis?

AS symptoms do not occur in all patients. These tend to get worse during the morning and the night, and may improve with exercise.

The main symptoms of AS are:

  • Back pain especially in the lower back. The pain lessens with exercise, but worsens with rest
  • Stiffness, which gets worse during the morning and the night and can prevent you from sleeping well
  • A painful inflammation where the bone is joined to a tendon or a ligament, called enthesitis can also occur, especially at the top of the shin bone, behind the heel (Achilles tendon), under the heel and where the ribs join to the breastbone
  • Fatigue is also a common symptom of AS, and results in tiredness and lack of energy

Additional information

You can find additional information about AS following these links:

NHS Choices:

National Ankylosing Spondylitis Association:

National Institute of Arthritis and Musculoskeletal and Skin Diseases:

1. Dean, E, et al. Rheumatology. 2013; 54(4), 650-657.