How Disc Degeneration Causes Back Pain
Disc degeneration may cause back pain when our intervertebral disc lose their height or when tears of the annulus occur, causing osteophytes or bone spurs.
As we reach our physical peak, our spine is fully developed and the discs between our vertebral bones are like brand new tires. In this analogy, the treads on the tires would be analogous to the discus annulus of out intervertebral discs and the fully inflated supply or air in the tires would be analogous to the nucleus pulposus of the intervertebral discs. Once these tires begin putting on a lot of miles on, the air eventually begins to seep out of the tires due to all the bumps and jolts from the road, and the treads begin to wear down. Eventually the tires may lose enough tread that the tires pop or begin to deflate at a rapid rate.
This same analogy roughly applies to the intervertebral discs of our spine, though the aging process is not so one sided, due to the ability to these discs to heal/regenerate themselves - to some extent. Unlike radial tires, our discs are filled with a pulpy fluid that contains water, proteoglycan aggrecans, glycosaminoglycan (GAG) chains of chondroitin sulfate, and other substances. When we are close to our physical peak, we have a healthy volume of water and other substances required to keep the discs filled and at heights tall enough to support the vertebral bones and other structures.
As we get older, the discs begin to lose their ability to retain water and nutrients as well as their ability to absorb water and nutrients from the bloodstream from nearby vessels. Eventually, more water is lost than is absorbed. While these changes occur within the interior of the disc, the annulus fibrosis, of fibrous outer layer of the disc may become worn weaken or frayed among several layers of its structure.
These two changes to the disc may affect our height and the structural integrity of the disc itself.
As the 23 discs begin to dry out, they lose their height gradually over each decade. The average person will have lost about an eighth of an inch of disc height along each individual disc by the age of 70. Collectively, this loss of disc height to all the discs will leave us two inches shorter than we were when we were 25. Beyond the obvious ego-bruising loss of height, how do these physical changes to our discs affect our healthy, and possibly cause us to have back pain. Remember that the main purpose of the discs are to act as shock absorbers for the spine. As weight as driven down on the spine, the discs taking on these added weights and pressure change their shape slightly, bulging outwards and downwards to absorb shock. When our disc ages, their consistency begins resembling a grape less and a raison more. Imagine taking the cushion out of a runners sneaker. When our discs fail to provide the shock absorbing properties they used to, we may feel back pain as a result. When our vertebrae are exposed to more pressures as a result, osteophytes (bony formations) may begin to form on the surfaces of the vertebral bodies that are in contact with the discs. Nerve endings near these osteophytes (bone spurs) may react by sending pain signals to the brain.
Next, learn what happens when the annulus of the disc tears.