Arthritis that occurs in the spine is often called facet joint arthritis because it primarily affects the facet joints.
The facet joints are small joints located in the back of the spine at each motion segment.
The breakdown of cartilage in the facet joints leads to loss of motion, pain and stiffness.
The word arthritis comes from a combination of the Greek "arthros," meaning a joint and "-itis," meaning inflammation. The facets are the only synovial joints in the spine, so spinal arthritis often refers to inflammation of the spinal facet joints.
How Facet Arthritis Develops
As mentioned, facet joints are synovial joints. This means that a delicate membrane, called a synovial membrane, encapsulates each facet joint.
The membrane produces a viscous, slippery fluid, called synovial fluid that lubricates the joint.
Examples of other synovial joints include shoulders, elbows, knees, hips, and knuckles. All synovial joints are susceptible to osteoarthritis.
There are dozens of facet joints in the spine, and they are almost always in motion and bearing weight. Over time, everyday stress can wear down a facet joint’s cartilage, causing it to thin out or disappear altogether.
In addition to daily wear and tear, other factors can also play a role in cartilage degradation, such as previous injuries to the joint, excess inflammation, and genetics.
Once a facet joint’s protective layer of cartilage is damaged or gone, the following process tends to occur:
- The facets’ bony surfaces rub directly against each other, causing friction and inflammation.
- The inflammation leads to changes in the joint’s soft tissues. For example, the facet joint’s synovial membrane thickens and produces less viscous - and less lubricating -fluid.
- The friction causes the vertebral bones to produce excess tissue, resulting in bone spurs and/or enlarged joints.
- The excess bone tissue then leads to more joint friction, causing a degenerative cycle of even more changes developing in the bone and surrounding soft tissues.
Facet joint arthritis is sometimes referred to by other terms, such as spondylosis, facet arthropathy, or facet joint degeneration.
