When damage is done to these discs, either from a single traumatic injury or from repetitive damage over time, the disc material can wear itself down causing bulging or herniation of the disc. When this happens, the disc protrudes into the spinal canal, decreasing the space and potentially putting pressure on the spinal cord. If the disc pressure is in the lower back, this can cause symptoms of shooting pain down the back of the leg and into the foot. This is also common in the neck where it can cause shooting pain in the arms and hand.
The disc is composed of two main parts: the annulus fibrosis and the nucleus pulposis. The annular fibers are the strong, outer covering of the disc designed for support and containing the nucleus pulposis. The nucleus pulposis is a jelly-like material found inside the disc. When a disc bulge occurs, this means that the jelly-like nucleus pulposis is putting pressure against the weakened annular fibers causing the disc to bulge into the spinal canal. When the disc is herniated, this means that the annular fibers have torn and allowed the jelly to escape its confinement and leak into the spinal cord. In either scenario, a bulge or herniation, the result is a decrease in space and an increase of pressure for the spinal cord.