Ankylosing spondylitis is a type of arthritis that affects the spine. The spine’s bones (vertebrae) fuse together, resulting in a rigid spine.

Ankylosing spondylitis (AS) is a long-term (chronic) condition in which the spine and other areas of the body become inflamed.

AS tends to first develop in teenagers and young adults. It’s also around three times more common in men than in women.