In their function as shock absorbers, intervertebral disc are constantly being compressed. If the anterior and posterior ligaments of the discs become injured or weakened, the pressure developed in the nucleus pulposus may be great enough to rupture the surrounding fibrocartilage (annulus fibrosis).
If this occurs, the nucleus pulposus may herinate (protrude) posteriorly or into one of the adjacent vertebral bodies. This condition is called a herniated (slipped) disc.
Most often the nucleus pulposus slips posteriorly toward the spinal cord and spinal nerves. This movement exerts pressure on the spinal nerves, causing considerable, sometimes very acute, pain.
If the roots of the sciatic nerve, which passes from the spinal cord to the foot, are pressured, the pain radiated down the back of the thigh, through the calf, and occasionally into the foot. If pressure is exerted on the spinal cord itself, some of its neurons may be destroyed.
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