The sciatic nerves are the largest in the human body. They run from the base of the lumbar spine, on either side, through the buttocks and down the back of the legs; they extend all the way to the feet. If the nerve-root becomes compressed, pain is often experienced, not only in the lumbar spine, but also radiating into the buttocks, hamstrings, and (occasionally) lower legs. The condition is referred to as sciatica, and it is very common.