The term sciatica refers to a certain type of radiculopathy that occurs in the leg. It is called sciatica because it describes the radiculopathy that occurs when one or more of the nerves that make up the large sciatic nerve are irritated or pinched. Therefore, sciatica is not any different than a pinched nerve anywhere else in the spine. It simply has its own name because it is fairly common. It also occurs in the lumbar spine, the most common site of spinal nerve irritation.
Sciatica is used to describe the pain that travels from the sciatic nerve in the lumbar region into your buttocks, back of the thighs, and sometimes calf and foot. The pain is typically caused by irritation of the nerve roots that join outside the spine to make up the sciatic nerve. Conditions that can cause sciatica are: herniated discs, bone spurs, cancerous tumors that are growing into the nerves, and fractures that put pressure on the nerves.