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 18 and 40 years of age.

You may not develop all of the main symptoms of AS if you have the condition.

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

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 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 is a common symptom of AS. It can make you feel tired and lacking in energy.

It's common for people with AS to also have other conditions, including:

• iritis, also known as acute anterior uveitis (where the front part of the eye becomes red and swollen)
• psoriasis
• inflammatory bowel disease (IBD)