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Ankylosing spondylitis (arthritis)

Ankylosing spondylitis (AS) is a form of inflammatory arthritis that affects the spine and sacroiliac joints (the joints in the lower back). Symptoms include chronic (long-term) inflammation, causing pain and stiffness in the back. In severe cases, the affected joints in the spine may become fused causing them to become inflexible and leading to a loss of movement in the spine. There may also be deformity or curving of the spine.  Treatment aims to minimize symptoms and prevent complications.

In most cases AS is a mild condition but, when severe, it can be debilitating. Nevertheless, the outcome in patients with AS is generally favourable compared with that in patients with similar conditions like rheumatoid arthritis.

AS can occur at any age, including in children. However, it is most likely to develop between the ages of 13 and 35 years and is uncommon after the age of 40 years. It affects men approximately three times more often than women. 


The exact cause of ankylosing spondylitis is unclear. It is thought to be an autoimmune disease - where the body’s own immune system attacks the body’s tissues causing inflammation and damage.

Genetic (inherited) factors appear to influence development of AS. In particular, people who have a gene called HLA-B27 are at much higher risk of developing AS.  Environmental factors may also play a role because AS does not develop in every person with the HLA-B27 gene.

There is some evidence that exposure to a certain intestinal bacterium stimulates an abnormal immune reaction, which results in the development of AS. 

Signs and symptoms

AS belongs to a group of inflammatory arthritic conditions of the spine called spondyloarthropathies. Unlike most other types of arthritis where the inside of the joint is inflamed, the spondyloarthropathies involve inflammation on the outside of the joint where the ligaments, joint capsule and tendons attach to bone (enthesis). In AS there is inflammation of the enthesis around the spinal and sacroiliac joints.

The most common early symptoms of AS are pain and stiffness in the back and neck. These are usually most noticeable in the early morning and tend to wear off during the day and with activity. Symptoms tend to develop gradually over a period of weeks or months but can sometimes develop rapidly.

AS can affect any part of the spine and may progress to the ribcage, causing chest pain that may be confused with angina or pleurisy. Sometimes joints such as the knee, and tendons (especially around the ankle), can be affected.

AS is a systemic condition, meaning it can have an impact on the whole body. Fatigue is commonly experienced and other symptoms may include mild fever, loss of appetite (with resulting weight loss) and night sweats.

In as many as 40% of patients inflammation of the eye, known as uveitis, is experienced. Up to 10% of patients may experience inflammation of the jaw. This can lead to difficulty with opening the mouth fully, making eating problematic.  In rare cases AS can be associated with problems in other parts of the body, including the heart, kidneys, lungs and nerves at the base of the spine.

AS is characterised by periods in which symptoms are absent (remission) and periods in which symptoms are problematic (relapses).


Early diagnosis of AS is important if fusion of the joints and permanent stiffening of the spine are to be avoided. It can be difficult to diagnose in the early stages as symptoms may be attributed to more common causes of back pain.   A doctor will evaluate the following when diagnosing the condition:

  • A full medical history, including any family history of AS
  • Discussion of current symptoms including a history of back pain
  • The age of the patient when the pain started
  • Physical assessment, including testing the range of motion in the patient's spine
  • X-rays
  • MRI (magnetic resonance imaging)
  • Blood tests – which may show the presence of the HLA-B27gene, a raised ESR (erythrocyte sedimentation rate) and a reactive protein which indicates inflammation.

In order for a diagnosis of AS to be made, a referral to a rheumatologist - who specialises in treating arthritis – may be recommended. 


While AS cannot be cured, treatment aims to minimise the symptoms and prevent long-term complications such as fusion of the joints. Severaldifferent medical professionals may be involved in treatment, including GP, rheumatologist, orthopaedic specialist, physiotherapist, occupational therapist, and podiatrist.  Essentially the goals of treatment are to:

  • Reduce inflammation
  • Reduce pain
  • Maintain mobility

To achieve these goals a combination of treatments is usually recommended. These include:

Medications used in the treatment of AS include non-steroidal anti-inflammatory drugs (NSAIDs) which work by treating pain and inflammation. These are vital in the treatment of AS and are usually very effective. Larger doses than normal are often required in the treatment of AS.

Pain relieving medications such as paracetamol may also be effective

Corticosteroid medications may also be used to reduce inflammation.  They can be given by tablet or may be injected directly into an inflamed joint

Biologic medications, known as “disease modifying medicines”, may be used in the treatment of severe AS. These medications help reduce pain, stiffness and tender or swollen joints, and improve function.  They are given by injection. The biologic medications that can be used for AS include adalimumab, etanercept, golimumab and infliximab.

Exercise is vital in the management of AS — especially exercise that maintains movement of the spinal joints and strengthens the muscles in the back and neck. Swimming is often recommended as it exercises all of these joints and muscles. A physiotherapist can recommend an appropriate exercise regimen. Individuals with AS also need to have periods of rest and avoid exhaustion.

Maintaining correct posture is vital for people with AS. Keeping the spine straight plays an important role in preventing complications. Using a firm mattress without pillows can help maintain correct posture when sleeping.

A physical therapist can design exercises specific to an individual person.  These exercises are likely to include range of motion and stretching exercises, which can help maintain flexibility in joints and preserve good posture.

Severe disability and deformity are unusual in AS but in cases where pain is extreme and deformities are disabling, surgery may be appropriate. Commonly this involves hip joint replacements. However, surgery to help straighten the spine may be required if curvature of the spine is severe.

Alternative therapies
Some people find therapies such as homeopathy, acupuncture and naturopathy are helpful in managing the symptoms of AS. Practising relaxation techniques such as deep breathing and meditation may also prove helpful

Not smoking, maintaining a healthy body weight and having a healthy balanced diet are also important factors in managing the condition. 

Further support

AS cannot be prevented but in most cases an independent life can be maintained. Research is continuing to try to understand the development of the disease so that in time a cure may be possible.  For further information and support please contact your GP or practice nurse, or contact Arthritis New Zealand:

Freephone: 0800 663 463 

For branch offices please refer to the local telephone directory or the Arthritis New Zealand website. 


Arthritis New Zealand (2016). Ankylosing spondylitis (Pamphlet). Wellington: Arthritis Foundation of New Zealand (Inc).
Brent, L.H. (2017). Ankylosing spondylitis and undifferentiated spondyloarthropathy (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. [Accessed: 26/07/17]
Mayo Clinic (2016). Ankylosing spondylitis (Web Page). Rochester, NY: Mayo Foundation for Medical Education and Research. [Accessed: 26/10/17]

Last Reviewed – October 2017 


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