How Ankylosing Spondylitis Works

While there is no definitive explanation for how ankylosing spondylitis is triggered, it is thought that genetic and/or environmental factors (such as exposure of a genetically susceptible individual to an unknown molecular substance, or an infection) can result in new and unnecessary bone formation – or ‘fibrosis’ – where bone connects to ligaments, tendons and joint capsules.

This process of new fibrosis creates inflammation, stiffness, and pain, eventually resulting in complete bone fusion in the sacroiliac joint, spine, pelvis and some other peripheral joints, such as the heel, Achilles tendon and the arch of the foot.