Ankylosing spondylitis is a form of chronic inflammation of the spine and the sacroiliac joints. The sacroiliac joints are located at the base of the low back where the sacrum. Chronic inflammation in these areas causes pain and stiffness in and around the spine, including the neck, middle back, lower back, and buttocks. Over time, chronic inflammation of the spine (spondylitis) can lead to a complete cementing together (fusion) of the vertebrae, a process referred to as ankylosis.
It is not known what causes the condition, but there is thought to be a link with a particular gene known as HLA-B27.
These fused spines are particularly brittle and vulnerable to breakage (fracture) when involved in trauma. Chronic spondylitis and ankylosis cause forward curvature of the upper torso (thoracic spine), which limits breathing capacity. Spondylitis can also affect the areas where ribs attach to the upper spine, further limiting lung capacity.
