What Is It?
The disks in your spine, called intervertebral disks, are thin, oblong structures that serve as cushions between the bones of your back (vertebrae). Each disk is made of a soft gel core surrounded by a tough, fibrous outer shell. This structure allows the disk to be firm enough to maintain the space between the vertebrae, but soft enough to compress when the spine flexes during bending, leaning and turning sideways.
In some people, mostly middle-aged adults, a disk's tough outer shell develops an area of weakness or a small tear. When this happens, part of the disk's soft inner core can bulge out of its normal position (herniate), producing a condition called a herniated disk. If the herniated disk presses on nerves in the nearby spinal canal, this can cause variety of nerve-related symptoms, including pain, numbness and muscle weakness. In the most severe cases, a herniated disk can compress nerves that control the bowel and bladder, causing urinary incontinence and loss of bowel control.
Scientists do not fully understand why disks herniate. Most theories attribute this condition to a combination of the following factors: