Sciatica is pain in the distribution of the sciatic nerve. This is typically felt on the back of the thigh and down the back of the leg. There are many potential causes of sciatica. These can include spinal stenosis, a ruptured or bulged disc, direct trauma to the nerve, and slippage of the vertebrae.
Spinal stenosis is a narrowing of the foramina, which is a passageway for nerves to exit the spinal canal. This is often a narrowing caused by osteoarthritis. It does not always cause problems.
The diagnosis of stenosis is done with an X-ray of the affected area of the spine. Sciatica is diagnosed through some simple exam maneuvers and by taking a careful patient history. For instance, on the exam, raising one leg (done by the examiner) while the patient is lying down will often reproduce pain on the side where there is sciatica.