Your spine is made up of vertebrae (bones) and disks. Disks are like soft cushions between the bones of the spine. The disks in the spine let you move your backbone.
When a disk between two bones in the spine presses on the nerves around the backbone, it’s called a herniated disk. The word “herniate” (say: her-nee-ate) means to bulge or to stick out. Sometimes this is called a ruptured or slipped disk. Herniated disks are most common in the lumbar spine, which is the lower part of your backbone, between the bottom of your ribs and your hips.
When part of a disk presses on a nerve, it can cause pain in the back and the legs. The location of the pain depends on which disk is weak. How bad the pain is depends on how much of the disk is pressing on the nerve. In most people with herniated disks, the pain spreads over the buttocks and goes down the back of one thigh and into the calf. This is known as sciatica because the pain travels along the path of the sciatic nerve. Some people have pain in both legs. In some people, the legs or feet feel numb or tingly.