What is ankylosing spondylitis?
Ankylosing spondylitis is an inflammatory rheumatic disease mainly affecting the spine, although sometimes other joints, ligaments and tendons are also affected. Ankylosing spondylitis affects more than 2.7 million adults and there is a tendency for it to run in families. The disease can affect people at any age but usually starts in people in their late teens and twenties. Most people develop symptoms before the age of 30. Only 5% get symptoms after 45 years of age.
In ankylosing spondylitis, inflammation occurs where ligaments or tendons meet joints. This inflammation is followed by some erosion of the bone where the joint or ligament is attached and eventually new bone growth occurs in these areas. Movement becomes restricted where the elastic tissue of ligaments or tendons is replaced by bone. Some or all of the joints and bones of the spine may fuse together, but it is rare for total fusion of the spine to occur. Most people will have only partial fusion, sometimes limited to the pelvic bones.
Onset of the disease is gradual with increasing back pain and stiffness over weeks or months rather than hours or days. As the disease progresses the symptoms may come and go. With the correct treatment and physical therapy the disease should not cause a stooping posture in later life.
What are the symptoms of ankylosing spondylitis?
The disease starts slowly, causing increasing pain and stiffness over weeks or months. Classically, the pain occurs in the lower back, buttocks and the backs of the upper thighs. In contrast with back strains or injuries, the pain and stiffness of ankylosing spondylitis improves with exercise and worsens with rest. The pain is usually worse in the morning and improves during the day. Initially, limitation of spinal movement may not be obvious, but as the disease progresses, changes to the bone structure occur and movements become more restricted. The pelvic joints are usually affected first. In 30% to 40% of patients, other joints such as the knees and ankles are also affected during the course of the disease. In 10% to 20% of patients, involvement of joints such as the knees, ankles, and feet is the presenting feature. In the early stages of the disease, some people may also feel generally unwell and may suffer from lack of sleep because of pain early in the morning. Weight loss may occur especially in the early stages and some people may feel feverish and experience night sweats. Ankylosing spondylitis can sometimes also affect the eyes, heart and lungs. These effects are not life-threatening and can be treated relatively easily. Most people with ankylosing spondylitis are able to lead a normal life and few need to make changes to their lifestyle or occupation.