Spinal discs act as connecting ligaments between the spinal vertebrae. Spinal discs also act as shock absorbers. The diagram to the left illustrates the inner portion of the disc, also known as the nucleus pulposis (pink) and the outer portion of the disc, also known as the annulus fibrosis (green).
Disc nucleus has been described as a ‘gelly’ substance and the annulus fibrosis has been described as tough fibrous ‘rings’.
This pressurized gelly center surrounded by rubbery fibrous rings allows for an ideal degree of motion, shock absorption, and strength.
Spinal discs are composed of living cells and these cells rely on normal daily activities and movements for their sustenance.
The diurnal variation of our existence (up when we are awake and recumbent when we sleep) allow for daily pumping, or loading and then unloading, to occur upon the disc. This creates a pumping mechanism which literally pulls nutrients, oxygen and waist products in and out of disc material–allowing for its sustained health.
If all goes well our discs last a lifetime and cause us zero issues.
Problems arise when discs experience excessive compressive forces or shearing forces. Accidents are known to injure discs. The combination of bending and rotating also often injures discs (especially those in the low back.)
Tears are known to often occur in the outer anular fibers of the disc. Remember, the inner nucleus of the disc (represented in pink in this diagram) is under pressure, creating the perfect shock absorber. With a torn annulus the inner pressurized jelly center of the disc may ooze outward into this tear.
Often initially this process is pain-free. But with time, inflammation, and increased outward migration of the nucleus, pain, numbness, or tingling may result.
Disc injuries and poor disc health is thought to be one of the primary causes of back pain and spinal disability.
A common scenario is that following a prolonged period of sitting, an individual will need to perform an activity. A combination bending forward and twisting places undue strain on the anular fibers and this can cause tearing.
Tearing of the annular fibers of a disc may not be felt or heard, at the moment. But like an ankle sprain, with time inflammation and associated swelling occurs and it is this inflammation and swelling which may cause noticeable symptoms.
With disc injuries and pain, the normal pumping mechanism within spinal discs is impeded, reducing the exchange of vital oxygen and nutrition to the cells of the anulus fibrosis and the nucleus pulposis and this sets up a degenerate process at that particular disc level of the spine. This can lead to degenerative disc disease (DDD).
DDD can be mild, moderate, or severe and can occur at one, or several, spinal levels.
The first diagram above illustrates that below and to either side of the disc are two L5 Spinal Nerve Roots (yellow). Notice the close proximity of the spinal nerve roots to the outer edge of the spinal disc. This could be problematic if the disc should tear and bulge or herniate outward toward either or both of these nerve roots.
When nerve roots in ones low back are pinched or inflamed by injured discs, several different symptoms may be noticed to include back pain, groin pain, hip pain, buttock pain, pain down the back of the thigh, pain behind the knee, leg pain, ankle pain or foot pain. Numbness or tingling may also be noticed.
One’s legs may give away or one may notice foot drop or weakness in other muscles supplied by these nerves.