This is a name given to pain, weakness, and sometimes tingling or numbness, along the course of the sciatic nerve. The nerve supplies the back of the thigh and most of the lower leg, ankle and foot, both for sensation and to drive the muscles. If the symptoms are in the front of the thigh or knee, it is unlikely to involve the sciatic nerve.
It is important on examination to try to work out at what point along the course of this long nerve it is being affected. There may be impingement of the nerve in the lumbar spine or the sacrum, which could be caused by a disc problem such as a herniation or prolapse; or more commonly a disturbance of joint function. It may be compressed where it comes out of the pelvis into the deep gluteal muscles behind the hip. Or there may be an irritation associated with injury or strain in the calf or hamstring muscles.
Often people describe buttock or leg pain as a more diffuse sensation in various sites from the low back down. Branches of the nerve transmit the sensation of pain but the tissues that are causing the symptoms may be more superficial muscles, or inflamed and painful joints supplied by branches of the nerve, setting up "referred pain" in other areas supplied by the nerve.
In certain, more severe, cases it may be necessary to refer the patient on for specialised examinations such as a scan to identify the cause of the problem. These cases are fortunately rare.