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 spinal inflammation (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.

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.

The diagnosis of ankylosing spondylitis is based on evaluating the patient's symptoms, a physical examination, x-ray findings, and blood tests. Symptoms include pain and morning stiffness of the spine and sacral areas with or without accompanying inflammation in other joints, tendons, and organs.

The examination can demonstrate signs of inflammation and decreased range of motion of joints. This can be particularly apparent in the spine. Flexibility of the low back and/or neck can be decreased. There may be tenderness of the sacroiliac joints of the upper buttocks. The expansion of the chest with full breathing can be limited because of rigidity of the chest wall. Severely affected persons can have a stooped posture.

The treatment of ankylosing spondylitis involves the use of medications to reduce inflammation and/or suppress immunity, physical therapy, and exercise. Medications decrease inflammation in the spine, and other joints and organs. Physical therapy and exercise help improve posture, spine mobility and lung capacity. Disease modifying drugs stop the illness from getting worse.