What Are Degenerative Changes?
Degenerative changes begin with an annular tear, in either a normal disc, or in one that has already begun to dessicate. Then, perhaps because of the increased stresses caused by the altered mechanics, or because of chemical assault caused by the inflammation, the rate of dessication accelerates.
In time, the facet joints will be affected. The facet joints will be subjected to increased wear-and-tear because the shock-absorbing function has been lost. In addition, as the disc continues to degenerate, disc space height will decrease.
The disc will, literally, collapse. Since the facet is comprised from the vertebrae above and below the disc, as the disc collapses, the two bone ends will slide past each other, causing malalignment. This is called facet subluxation. Such malalignment will result in even greater wear-and-tear on the facets.
The articular cartilage of the facets is the smooth covering of the bone ends that allows them to flow smoothly over each other trillions of times throughout our lifetime. Increased wear-and-tear and malalignment damages the articular cartilage until the facet joint is bone on bone. The loss of articular cartilage is, by definition, degenerative arthritis.
The body responds to the irritation produced by the loss of articular cartilage by increasing the lining of the capsule around the facet joint called the synovium.
This is called synovial hypertrophy. The synovium then increases it’s production of fluid. This is designed to decrease the painful, bone-on-bone, motion. Unfortunately, the increased fluid results in a condition, that itself, is painful, called an effusion. “Water-on-the-knee” is an example of an effusion.
As the deterioration continues, the body will take even more drastic measures in an attempt to decrease the abnormal motion, not only at the facet joints, but at the disc space, as well. The body will increase the surface area of the joint, which, in turn, increases the frictional forces between the joint surfaces in order to decrease motion. In effect, by “fusing” the joint. It does this by producing osteophytes, or “bone spurs”.
Producing osteophytes however, causes narrowing of the spinal canal and constriction (“pinching”) of the nerves left in the canal. Osteophytes also narrow the “holes” that the nerves exit the spinal column from.
These “holes” are called foramen. The foramen have already been narrowed by the collapse of the disc. This point in the degenerative process is known as spinal stenosis. Stenosis is the medical term for narrowing.
Note that, all the events that take place, from the initial insult to the disc, to the end-result, spinal stenosis are referred to as “degenerative changes”. These changes take place over decades. And, the rate, at which they occur is variable, and depend to a certain extent, on the person’s lifestyle and activities. The term “degenerative changes” can be confusing because there is certainly a difference between a “degenerative disc” that has only recently begun to dessicate, and the end-result of spinal stenosis.
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