Ankylosing spondylitis is a chronic inflammatory rheumatic disease which affects the sacroiliac joints and the spinal cord. This disease occurs most often in young men, and is responsible for pain in the buttocks and the lower back, mainly occurring at night and upon waking in the morning, diminishing throughout the day, but returning while at rest. The joints in the spinal cord and the back part of the pelvis become more and more stiff, which leads to the ankylosis. The progression of this illness is long and comes in spurts. X-rays of the spine can help with a diagnosis. The treatment uses anti-inflammatory analgesics and local injections can lessen the pain during the spurts. Other medications are used for advanced stages.