What Is a Herniated Disk?

The bones of the spine (vertebrae) are each cushioned by small disks. These flat, round disks have a tough outer layer, the annulus, surrounding a jellylike material inside, called the nucleus.

As we age, our disks can lose fluid and become dried out, causing the disk to compress. This may lead to the deterioration of the outer annulus, allowing the nucleus to bulge out. This is called a bulging disk.

As the disk continues to degenerate, or with continued stress on the spine, the inner nucleus may actually rupture out from the annulus. This is considered a ruptured, or herniated, disk. The fragments of disk material can press on the nerve roots located just behind the disk space, causing pain, weakness, numbness or changes in sensation.

Herniated disks can occur in any part of the spine, although they are more common in the lumbar spine (lower back). They can also occur in the cervical spine (neck).