The spine is made up of bones (vertebrae) cushioned by small oval pads of cartilage and disc. These consist of a tough outer layer (annulus) and a soft inner layer (nucleus). A herniated disc, sometimes called a slipped or ruptured disc, occurs when a small portion of the nucleus pulposus pushes out through a tear in the annulus into the spinal canal. This can irritate nerves and result in pain, numbness or weakness in the back, legs or arms. In some it can even put pressure on the spinal cord resulting in more advanced symptoms.
Many sufferers report back pain which radiates down the leg or arm, making everyday activities difficult or even intolerable.