Ankylosing spondylitis (AS) is a form of inflammatory arthritis that affects the spine and sacroiliac joints in the lower back.
The main symptoms are pain and stiffness in the back, but AS can also cause a range of problems elsewhere in the body. Treatment aims to minimize symptoms and prevent complications.
AS can occur at any age, including in children. However, it is most likely to develop between the ages of 15 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 AS is unclear. It is thought to be an autoimmune disease — where the body’s immune system attacks the body’s tissues causing inflammation and damage.
Genetic (inherited) factors appear to influence development of AS. Environmental factors may also play a role - 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
The most common early symptoms of AS are pain and stiffness in the lower back and hips. 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 is a systemic condition, meaning it can affect the whole body. Fatigue is commonly experienced and other symptoms may include mild fever, loss of appetite (with resulting weight loss), and night sweats.
AS can affect different parts 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 many as 40% of patients may experience symptoms of eye inflammation, including – pain and redness. Up to 10% of patients may experience inflammation of the jaw, making it difficult to eat or open the mouth fully. 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). In most cases AS is a mild condition but, when severe, it can be debilitating.
Early diagnosis of AS is important to prevent fusion of the joints and permanent stiffening of the spine. However, AS 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
- MRI (magnetic resonance imaging)
- Blood tests — which can detect inflammation and genetic information.
Diagnosis of AS may require referral to a rheumatologist — a doctor who specialises in treating arthritis.
Because AS cannot be cured, treatment aims to minimise the symptoms and prevent long-term complications such as fusion of the joints. Several different medical professionals may be involved in treatment, including GP, rheumatologist, orthopaedic (spine and joint) 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 swelling, and improve function. They are given by injection.
Exercise and self help
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.
A physical therapist can design exercises specific to an individual person. These exercises are likely to include range of motion and exercises, which can help maintain flexibility in joints and preserve good posture when standing and sitting.
Applying heating pads to stiff joints and tight muscles and taking a hot bath can ease pain and stiffness. Icing inflamed joints can help to reduce swelling.
Not smoking, maintaining a healthy body weight, and a healthy balanced diet may help to avoid the worst outcomes associated with AS.
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.
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 talk to your GP or practice nurse, or contact Arthritis New Zealand.
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 PDF). Wellington: Arthritis Foundation of New Zealand (Inc). https://www.arthritis.org.nz/wp-content/uploads/2018/10/AS.pdf
Brent, L.H. (2020). Ankylosing spondylitis and undifferentiated spondyloarthropathy (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/332945-overview [Accessed: 30/10/20]
Mayo Clinic (2019). Ankylosing spondylitis (Web Page). Rochester, MN: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/ankylosing-spondylitis/symptoms-causes/syc-20354808 [Accessed: 30/10/20]
Last Reviewed: October 2020