Ankylosing spondylitis (AS) is a type of chronic inflammatory arthritis that primarily affects the spine and the sacroiliac joints at the base of the spine. This condition can lead to severe, chronic pain and discomfort. Over time, AS can cause some of the vertebrae in the spine to fuse, leading to stiffness and a rigid spine.

Unlike some other forms of arthritis, AS often starts in early adulthood and is more common in men than in women. The exact progression and severity of the condition can vary significantly from person to person. Treatment and lifestyle modifications can help manage symptoms and improve quality of life.