Ankylosing spondylitis


Caption: Photograph of a young man suffering from severe ankylosing spondylitis, showing kyphosis (outward curvature) of the spine due to fusion of the vertebrae

What is ankylosing spondylitis?

Ankylosing spondylitis is a form of chronic inflammation of the spine and the sacroiliac joints. The sacroiliac joints are located in the low back where the sacrum (the bone directly above the tailbone) meets the iliac bones (bones on either side of the upper buttocks). Chronic inflammation in these areas causes pain and stiffness in and around the spine. Over time, chronic inflammation of the spine (spondylitis) can lead to a complete cementing together (fusion) of the vertebrae, a process referred to as ankylosis. Ankylosis leads to loss of mobility of the spine.

Ankylosing spondylitis is considered one of the many rheumatic diseases because it can cause symptoms involving muscles and joints.
Ankylosing spondylitis:

  1. Is two to three times more common in males than in females.
  2. In women, joints away from the spine are more frequently affected than in men.
  3. It affects all age groups, including children.
  4. The most common age of onset of symptoms is in the second and third decades of life.


  • What causes ankylosing spondylitis?

The tendency to develop ankylosing spondylitis is believed to be genetically inherited, and a majority (nearly 90%) of people with ankylosing spondylitis are born with a gene known as the HLA-B27 gene.

  • What are ankylosing spondylitis symptoms?

The symptoms of ankylosing spondylitis are related to inflammation of the spine, joints, and other organs. Fatigue is a common symptom associated with active inflammation. Inflammation of the spine causes pain and stiffness in the low back, upper buttock area, neck, and the remainder of the spine. The onset of pain and stiffness is usually gradual and progressively worsens over months. Occasionally, the onset is rapid and intense. The symptoms of pain and stiffness are often worse in the morning or after prolonged periods of inactivity. The pain and stiffness are often eased by motion, heat, and a warm shower in the morning.
Those who have chronic, severe inflammation of the spine can develop a complete bony fusion of the spine (ankylosis). Once fused, the pain in the spine disappears, but the affected individual has a complete loss of spine mobility.

Chronic spondylitis and ankylosis cause forward curvature of the upper torso (thoracic spine), which limits breathing capacity. Ankylosing spondylitis can cause inflammation and scarring of the lungs, causing coughing and shortness of breath, especially with exercise and infections. Therefore, breathing difficulty can be a serious complication of ankylosing spondylitis. Other areas of the body affected by ankylosing spondylitis include the eyes, heart, and kidneys. 


Caption: Fused knee joint. Coloured X-ray of a knee joint showing fusion of the bones. The femur (thigh bone, top) is touching the tibia (shin bone, lower right), and the bones have grown together. This leads to immobility of the joint. At lower left is the fibula, the smaller lower leg bone. The fusion of a joint can be a symptom of severe arthritis. It usually occurs in the back (where it is known as ankylosing spondylitis), but can occur in the knee or hip joints, as well as others.