What is Degenerative Disk Disease?
It is a process that essentially means the spine is aging. In my opinion, it should never had been classified as a disease, as it affects all of us, if we live long enough. In one of my earlier blogs, I reviewed medical research that demonstrated that disk disease or degeneration has been identified in young adults at a great rate than originally thought.
So what is this process?
Before we discuss degenerative disk disease, we must first understand the function of the disk. The disk is a soft tissue that serves as a shock absorber, allowing the stacked bones called the vertebrae to remain oriented next to each other, without breaking due to the forces. The disk also acts as a ligament, that allows the the vertebra to move, bend, and twist, while maintaining its shape and function. And finally, the disk acts as a spacer, so the nerves can exit out the vertebral canal, out the holes called the foramen, without causing undue pinching of the nerves as they exit.
In the diagram, you can see the anatomy of the vertebrae, and see the relationship between the vertebral bone and the disk. If you could imagine, the disk allow the proper space to be maintained within the foramen. You can see how important this relationship will be, in order to avoid excessive pinching or stretching of the nerves. The disk height is also important in maintaining the proper relationship of the facet joints. With any change in the disk height, it will effect all these relationships.
In the degenerative disk disease process, the disk begins to lose its water content. The process actually starts early in life. The disk in essentially make up of two components. The outer part of the disk is called the annulus. It is a woven firm cartilage layer that contains the second part of the disk called the nucleus. The nucleus is soft, and early in life, gelatinous in consistency. To make an analogy, it is like a jelly donut, where the “bread” outside is the annulus, and the “jelly” inside is the nucleus.
To clarify the statement above, the “jelly” loses its water content, and the “jelly’ becomes firmer, and less fluid. In addition. Due to the loss of water content, the disk height starts to shrink, or narrow. Disk narrowing leads to foramen narrowing, thus potentially causing pinching of the nerve.
Disk narrowing also changes the orientation of the facet joints, causing potential abnormal rubbing of the facet bones against another. This can lead to the enlarging of the bones by the rubbing. This is the beginnings of the so called facet arthropathy. This is the “bones spurs” pinching the nerve.
Also, as the disk narrows, the sidewalls of the disk bulge out, similar to the car tire sidewalls bulging out as air slowly leaks out of the tire. This bulging can potential also cause the pinching of the nerve.
Also, as the disk narrows, it allows the vertebra to move more than when the disk is at normal height. Again, it is like the car tire, that is not fully inflated. There is more movement, or bounce. This extra movement can cause increased wear of the annulus, and potentially making rupture of the annulus, and disk herniation more likely.
The degenerative disk disease process is progressive, and ultimately can cause symptoms such as back pain, nerve pinch pain, and stiffness. This is actually the process that is occurring everyday to everyone. This is the process of spine aging. Fortunately, most of the time, the pain associated with the process is temporary, and not severe.
- Shevelev IN, Konovalov NA, Cherkashov AM, Molodchenkov AA, Sharamko TG, Asiutin DS, Nazarenko AG. [Virtual clinical diagnosis support system of degenerative stenosis of the lumbar spinal canal]. Zh Vopr Neirokhir Im N N Burdenko. 2013;77(5):38-43; discussion 43. PubMed PMID: 24564084