Sciatica - Pain along the large sciatic nerve that runs from the lower back down through the buttocks and along the back of each leg. This is a relatively common form of back pain. Sciatica is usually caused by pressure on the sciatic nerve from a herniated disc (also referred to as a bulging disc, ruptured disc or pinched nerve). The problem is often diagnosed as a "radiculopathy", meaning that a disc has protruded from its normal position in the vertebral column and is putting pressure on the radicular nerve (nerve root).