What Is It? Ankylosing spondylitis is a form of arthritis that
mainly affects the lower back. It causes inflammation and damage
at the joints, and first affects the sacroiliac joints between
the spine and the pelvis. It also can affect other areas of the
spine and other joints, such as the knee. Eventually, inflamed
spinal joints can become fused, or joined together so they can't
move independently. The word spondylitis refers to inflammation
of the spine; ankylosis means fusion or the melding of two bones
into one. Ankylosing spondylitis is relatively rare. It affects
about 1 in 1,000 people. It may run in families, although its
cause is not understood. It most commonly strikes otherwise
healthy young men. Men get this condition 10 times more often
than women. The disorder most often appears between the ages of
20 and 40, but can develop in children. A person with ankylosing
spondylitis commonly will feel pain or stiffness in the lower
back, especially in the morning or after periods of inactivity.
Usually,