Ankylosing Spondylitis (AS) is an inflammatory arthritis, autoimmune condition that primarily effects the spine and pelvic joints, causing fusion.
Inflammation is part of the immune system function of our bodies used to fight diseases. In autoimmune conditions the body is a bit confused, and is actually fighting itself. :(
The inflammation seen in AS occurs in the part where the tendons and ligaments join the bone. This type of inflammation is called enthesitis.
When the continued inflammation of the joining point, has actually damaged the bone, the immune system rebuilds it. Unfortunately this leads to bony growths, called syndesmophytes. That then cause further issues for the tendons and ligaments by stiffening and weakening them. Overtime this calcification can lead to a complete fusion of the joint, particularly occurring in the spine joints.
That is why reducing/stopping the inflammation is the Dr's first priority when managing a patient's AS.
For more on AS Symptoms, click here.