Ankylosing spondylitis (AS) is a long-term (chronic) condition in which the spine and other areas of the body become inflamed. The symptoms of AS can vary but usually involve: back pain and stiffness that improves with exercise and isn't relieved by rest pain and swelling in other parts of the body, such as the hips, knees and ribs fatigue (extreme tiredness) These symptoms tend to develop gradually, usually over several months or years, and may come and go over time. In some people, the condition gets better with time, but for others it can get slowly worse.