The sciatic nerve extends from the lower back and down the back of each leg. Sciatica is the pain you get when this nerve is pinched or pressure exerted on it in some way, usually by a herniated disc. No particular injury causes sciatica, it is mostly because of the wear and tear of the lower spine.
Sciatica can be pretty debilitating. It is a relentless pain and can affect one whole side of the lower back, buttock, thigh, leg, and foot. You will find it difficult to sit, and experience a shooting pain when you try to stand. The pain will be constant and may be accompanied by a lower backache as well.