To define spondylitis, it is helpful to understand the roots from which this word originated. The term spondylitis derives from the Greek word spondylo, or vertebra. The suffix -itis is a common medical suffix used to denote inflammation (e.g., appendicitis is the inflammation of the appendix). If we put the two together, we see that spondylitis is inflammation of the vertebrae – one of the characteristics that define spondylitis.
Spondylitis is a term that actually encompasses a group of conditions affecting the joints of the spine (called facet joints, which are located between the vertebrae), and also the joints between the spine and the pelvis (sacroiliac joints). Spondylitis may affect other joints in the body, too.
Traits of Spondylitis
Spondylitis is a synonym for spondyloarthritis and spondyloarthropathy. All are blanket terms for conditions displaying these traits:
- Inflammation of the spine, sacroiliac joints, and other joints
- The attachment of ligaments to the bone
- The lack of other signs or markers that might indicate other types of arthritis
Example: Ankylosing Spondylitis
Ankylosing spondylitis (AS) is a particularly debilitating form of spondylitis often characterized by inflammation in the spinal joints (as well as other joints) that can lead to bone growth and – eventually – to spine fusion. Typically, AS first makes itself felt in the lumbosacral region (that is, the lower back) due to stiffness and inflammation in the sacroiliac joints. These joints mark the union of the spine and the pelvis, as the sacrum (lower spine) and each ilium (hip bone) come together here. Though the reasons why it starts in the sacroiliac are hard to define, spondylitis of this sort is understood to be largely hereditary in nature.
As mentioned above, the inflammation of this condition can lead to the fusing of bone, but it can also result in enthesis, which is a type of inflammation that can lead to the attachment of joint capsules and ligaments to the bone. Gradually, these areas may then develop into bony overgrowths – the process known as ankylosis. The resulting loss of movement, coupled with the inherent fragility of such bone, increases the risk of fracture. The good news is that this stage of ankylosing spondylitis is much less common.