Ankylosing means fusing together. Spondylitis indicates inflammation of the vertebrae. Anklylosing Spondylitis describes a condition when some or all of the joints and bones of the spine fuse together. Classified as a rheumatic disease, ankylosing spondylitis mainly affects the spine but it can also affect other joints, tendons and ligaments in the body. It can also spread to the lungs, bowels and heart.
Usually, inflammation occurs at the site where certain ligaments or tendons attach to bone (enthesis). Some erosion of bone at the site of the attachment (enthesopathy) follows this. As the inflammation subsides, a healing process takes place and new bone develops. Movement becomes restricted where bone replaces the elastic tissue of ligaments or tendons. Repetition of this inflammatory process leads to further bone formation causing backbones and vertebrae to fuse together. This immobile condition often leads to nerve damage and back pain.