Disc Facts and Fallacies

January 26, 2008

The term “slipped disc” is commonly used to describe a multitude of back pains and problems. A look at the composition and function of a disc explains why it doesn’t really slip, and why discs shouldn’t carry the blame for everything that goes wrong with our backs.

The Composition And Function Of A Disc

Each vertebra in your spine is separated from its neighbor by a cushion of cartilage called a disc. The annulus fibrosa, the outer ring of the cushion, is dense and layered with criss-crossed fibers, like the covering of a radial tire. The interior cartilage, the nucleus pulposus, is soft and squishy, like thick jelly.

The disc is located between two vertebrae. It does not slip out of position. Rather, the disc may bulge out from between the vertebrae. A disc serves as a hydraulic shock absorber. One third of the spine’s height is made up of discs. In the lower back the nucleus is located slightly to the rear of the vertebral bodies, making it quite vulnerable to injury.

Healthy Discs

Healthy discs compress and release, like springs. They serve as flexible spacers between vertebrae, giving all the bony parts and tissues of the vertebral joint room to breathe and move. At night, when our discs are free from gravity’s pressure, they soak up nutrients and water from the blood, making the average person as much as two inches taller in the morning.

Aging Discs

As we age, our discs lose moisture. Their cellular activity slows down, which means their ability to regenerate after injury or disease is reduced. As the disc loses moisture it also loses height, which stimulates the growth of osteophytes within the vertebrae, and can put pressure on nerves. This can also affect the alignment of the facet joints. There’s some good news about aging discs. As the disc center loses moisture and diminishes, less pressure is put on the annulus, which makes a tearing or crack of the disc covering less likely.

Herniated Disc

When the disc covering weakens before its center has dried out, the pressure from the center can cause the annulus to crack or rupture. The nucleus pulposus oozes out and may push against a nerve, often causing severe pain. The protrusion can be mild or sever, depending upon how much of the disc center escapes, and what it presses against. A herniated disc is the most severe disc problem and can be caused by a sudden injury trauma. Sometimes surgery is the only solution for a herniated disc.

Bulging Disc

A bulging disc does not involve an annulus crack or rupture. The bulging disc can irritate a nerve root or ligament without disturbing its function. This pain tends to come and go, and is often brought on by bending forward, which puts stress on the rear wall of the spinal column.


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