Degenerative Disc Disease

Degenerative disc disease is one of the most common causes of low back pain, and also one of the most misunderstood.

Degenerative Disc Disease is a Misnomer:

A large part of many patients’ confusion is that the term “degenerative disc disease” sounds like a progressive, very threatening condition. However, this condition is not strictly degenerative and is not really a disease:

  • Part of the confusion probably comes from the term "degenerative", which implies to most people that the symptoms will get worse with age. The term applies to the disc degenerating, but does not apply to the symptoms. While it is true that the disc degeneration is likely to progress over time, the low back pain from degenerative disc disease usually does not get worse and in fact usually gets better over time.
  • Another source of confusion is probably created by the term "disease", which is actually a misnomer. Degenerative disc disease is not really a disease at all, but rather a degenerative condition that at times can produce pain from a damaged disc.

Disc degeneration is a natural part of aging and over time all people will exhibit changes in their discs consistent with a greater or lesser degree of degeneration. However, not all people will develop symptoms. In fact, degenerative disc disease is quite variable in its nature and severity.

Medical Practitioners Disagree on Degenerative Disc Disease:
Finally, many patients are confused about degenerative disc disease because many medical professionals don’t agree on what the phrase describes.

In practical terms, this means that few practitioners agree on what does and does not constitute a diagnosis of degenerative disc disease. Even medical textbooks don’t usually attempt to give an accurate description. Therefore, while many practitioners believe that degenerative disc disease is a common cause of low back pain in young adults, very few agree on the implications.

While there is still a lot of debate in the medical community about degenerative disc disease, a few aspects of the condition are known. This article will discuss aspects of degenerative disc disease that are more commonly accepted, such as the theory of the degenerative cascade, as well as some areas of theory that are still a source of debate in the medical community.

Pain from Degenerative Disc Disease:
The lumbar disc is a unique and well-designed structure in the spine. It is strong enough to resist terrific forces in multiple different planes of motion, yet it is still very mobile. The disc has several functions, including acting as a shock absorber between the vertebral bodies.

The lumbar disc has been likened to a jelly donut. It is comprised of a series of bands that form a tough outer layer and soft, jelly-like material contained within:

Annulus fibrosus—the disc’s firm, tough outer layerNerves to the disc space only penetrate into the very outer portion of the annulus fibrosus. Even though there is little innervation to the disc, it can become a significant source of back pain if a tear in the annulus reaches the outer portion and the nerves become sensitized. With continued degeneration, the nerves on the periphery of the disc will actually grow further into the disc space and become a source of pain.

The nucleus pulposus contains a great deal of very inflammatory proteins. If this inner disc material comes in contact with a nerve root, it will inflame the nerve root and create pain down the leg (sciatica or radiculopathy). In the same manner, if any of the inflammatory proteins within the disc space leak out to the outer annulus and touch the pain fibers in this area, it can create a lot of low back pain.

Source of the Pain:

Generally, the pain associated with degenerative disc disease is thought to stem from two different factors:

  • Inflammation
  • Abnormal micromotion instability

The proteins in the disc space can cause a lot of inflammation, and inflammation in the disc space can lead to low back pain radiating to the hips. The associated pain can also travel down the back of the legs.

If the annulus—the outer rings of the intervertebral disc - becomes damaged or worn down, it is not as effective in resisting motion in the spine. This condition has been termed “micromotion” instability because it is usually not associated with gross instability (such as a slipped vertebral body or spondylolisthesis).

Both the inflammation and micromotion instability can cause muscular spasm in the low back. The muscle spasm is the body’s attempt to stabilize the low back. It is a reflex, and although the body’s response of muscle spasm is not necessary for the safety of the nerve roots, it can be quite painful.

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