Ankylosing spondylitis

Chronic, progressive, painful

Ankylosing spondylitis (AS) is a chronic, progressive, painful form of inflammatory arthritis, which affects mainly the spine and sacroiliac joints (the joints where the spine attaches to the pelvis). It can also affect other joints, tendons and ligaments.

Ankylosing means stiffening and fusing while spondylitis means inflammation of the spine. Ankylosing spondylitis describes the condition where some of the joints and bones of the spine become fused together because of inflammation.

Symptoms of ankylosing spondylitis

  • A slow or gradual onset of back or buttock pain over weeks or months instead of suddenly
  • Early morning stiffness or pain that wears off during the day as you move about
  • Persistent back pain that last for more than three months
  • Feeling better after exercise and worse after rest, particularly at night
  • Tiredness and Fatigue
  • Loss of appetite, weight loss
  • Mild fever, especially in the early stages
  • Pain that is dull and persistent on one or both sides of the body
  • Pain that starts in or spreads to a peripheral joint
  • Iritis or Uveitis, inflammation of the eyes
  • Bowel inflammation associated with Crohn’s disease or ulcerative colitis

Not everyone will experience all these symptoms because the course of ankylosing spondylitis varies greatly from individual to individual.

About 30% to 40% of people with AS will experience anterior uveitis (also called iritis), which is inflammation of the middle layer of the eye. Also, about 10% of those with AS will develop inflammatory bowel disease (IBD). There are extra-articular manifestations of AS, which may or may not be experienced.

Learn More

Read more about extra-articular manifestations (EAMs) of ankylosing spondylitis in this article written by Dr. Dinny Wallis, MBChB.

Diagnosis of ankylosing spondylitis

If you are 45 years of age or younger and have had persistent back pain for more than three months, there is a chance that you have inflammatory rather than mechanical back pain. They can be difficult to differentiate, especially in the early stages of inflammatory back pain and particularly because back pain is one of the most common complaints that people take to their family doctor.

Usually a referral to a rheumatologist is required for a diagnosis.

There is no single definitive test for AS or any of the spondyloarthritis diseases.

The rheumatologist will conduct a thorough physical exam; take a medical history including any family history of AS, order blood tests including a test for the gene HLA-B27, and order X-rays.

In the past a diagnosis of AS was confirmed by the presence of sacroiliitis (sclerosis and erosion of the sacroiliac joints) in X-rays. In addition, the physical exam would have revealed any sites of inflammation and limitations in spinal mobility.

Lastly, the medical history would have revealed whether any of the symptoms listed above are present. All these symptoms and information would lead to an informed diagnosis of AS. The presence of HLA-B27 gene increases the likelihood of a diagnosis of AS but only 2% to 4% of all HLA-B27 positive individuals develop AS.

One of the difficulties of the diagnosis is the confirming X-ray. This is because damage to the sacroiliac joints typically does not show up on X-rays initially.

The interpretation of the sacroiliac joints is difficult and evidence of sacroiliitis could be easily missed. This led to many people waiting several years for a diagnosis.

It is not uncommon to hear of people suffering for 10 to 20 years before they were properly diagnosed. Even today, about half of the people with AS end up waiting five or more years for their diagnosis.


Learn about the management of ankylosing spondylitis (AS).