Degenerative disc disease in the lumbar spine, or lower back, refers to a syndrome in which a compromised disc causes low back pain.
Although there is a slight genetic component to individuals who suffer from DDD, the true cause is probably multifactorial. It could be from simple wear and tear, or may have a traumatic cause. However, it rarely starts from a major trauma such as a car accident. It is most likely due to a low energy injury to the disc that progresses with time.
The disc itself does not have a blood supply, so if it sustains an injury it cannot repair itself the way other tissues in the body can. An otherwise insignificant injury to the disc can start a degenerative cascade whereby the disc wears out. Despite its rather dramatic label, degenerative disc disease (DDD) is fairly common, and it is estimated that at least 30% of people aged 30-50 years old will have some degree of disc space degeneration, although not all will have pain or ever receive a formal diagnosis. In fact, after a patient reaches 60, some level of disc degeneration is a normal finding on an MRI scan, rather than the exception.
Lumbar DDD Causes
The low back pain associated with lumbar degenerative disc disease is usually generated from one or both of two sources:
- Inflammation, as the proteins in the disc space irritate the surrounding nerves - both the small nerve within the disc space and potentially the larger nerves that go to the legs
- Abnormal micro-motion instability, when the outer rings of the disc, called the annulus fibrous, are worn down and cannot absorb stress on the spine effectively, resulting in movement along the vertebral segment (See Figure 1).
Excessive micro-motion, combined with the inflammatory proteins, can produce ongoing low back pain.
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Fortunately, over a long period of time the pain from lumbar degenerative disc disease eventually decreases, rather than becoming progressively worse. This is because a fully degenerated disc no longer has any inflammatory proteins (that can cause pain) and usually collapses into a stable position (see Figure 2), eliminating the micro-motion that generates the pain.
Because of this process, even patients who experience severe pain and frequent flare-ups in their 40’s may find that their back pain is almost gone when they are in their 60’s. Although back pain from osteoarthritis is common in our later years, it is not often from the disc space itself.
- See Lumbar Degenerative Disc Disease Diagnosis for a more in-depth discussion