Ankylosing spondylitis is a chronic inflammatory disease that is most often characterized by back pain and stiffness. While this form of arthritis commonly affects the spine, the disease can also develop in the shoulders, hips, knees, and other joints. Ankylosing spondylitis may also affect the eyes, lungs, and heart. Men are more likely than women to get the disease, which may begin in adolescence. The exact cause or causes of the disease are unknown. Some risk factors for ankylosing spondylitis include being male, having a family history of the disease, and possessing a certain genetic variation.