Spondylitis Association of America

Ankylosing spondylitis (AS) is a type of arthritis from the disease spectrum of axial spondyloarthritis. The term comes from the Greek ankylos meaning crooked, curved or rounded, spondylos meaning vertebra, and -itis meaning inflammation. It is characterized by long-term inflammation of the joints of the spine, typically where the spine joins the pelvis. Lower back pain is a hallmark, but eye and gastrointestinal problems and arthritis of other joints may also occur. Joint mobility in the affected areas often worsens over time, though the progression of symptoms varies significantly.