Your spine is made up of a column of bones with a space in the center for the spinal cord called the spinal canal. Disks between the vertebra act as shock absorbers when you move your back. A ruptured disk, also called a herniated or bulging disk, or a narrowed spinal canal, termed spinal stenosis, can put pressure on or irritate the sciatic nerve. This nerve, actually a group of nerves, runs from the lower spine, down the leg to the foot. Irritation of the sciatic nerve is known as sciatica and can cause pain, numbness, or tingling in the leg.