what causes ankylosing spondylitis
About Ankylosing Spondylitis. Ankylosing spondylitis is a form of progressive arthritis due to chronic inflammation of the joints in the spine. Its name comes from the Greek words  ankylos,  meaning stiffening of a joint, and  spondylo,  meaning vertebra.nkylosing Spondylitis. A form of arthritis that affects the spine, the sacroiliac joints, and sometimes the hips and shoulders. In severe cases, the joints of the spine fuse and the spine becomes rigid. PubMed Health Glossary. (Source: NIH-National Institute of Arthritis and Musculoskeletal and Skin Diseases).