Spinal Disc Disease

Spinal disc anatomy

The disc is made from two separate parts.  There is a soft center called the nucleus and a hard fibrous shell called the annulus.  The disc is made to support the weight of the body and provide a pad to cushion movements like bending and twisting.

Diagram of spinal disc - nucleus, annulus
Diagram of a normal spinal disc

Normal spinal disc

When we stand, there is a downward pressure on each of the discs.  The downward pressure is distributed by the normal disc.  The pressure on the annulus should be distributed evenly around the disc.  In addition to distributing the pressure, the annulus prevents the nucleus from leaking.

Bulging spinal disc

If the annulus becomes weak, the pressure is no longer distributed.  The pressure in the back, or posterior portion of the disc, becomes higher and the annulus bulges outward.  The bulge causes pain and can cause a pinched nerve.

Diagram of a bulging spinal disc
Diagram of a herniated spinal disc

Herniated spinal disc

If the bulging disc deteriorates still more, the annulus can rip open and the center, or nucleus of the disc, can leak out.  This leakage is called a herniation.  In addition to back pain from the torn disc annulus, there is frequently a pinched nerve.  This causes leg pain.

Go to the next pain on Pinched Nerves.

Go to the next chapter on symptoms.

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Last modified: 07/27/08