Dad called and said he has back pain that is now going down his leg. He says it's sciatica? How do they know for sure what's causing the leg pain?

Sciatica isn't really a diagnosis as much as it's a set of symptoms. Low back or buttock pain that travels down the leg (sometimes all the way down to the foot) is the usual complaint. The sciatic nere is usually involved, which is why the condition is called sciatica.

Pressure on (or irritation of) the sciatic nerve or any of the spinal nerve roots that make up the sciatic nerve can lead to sciatica. The symptoms can be mild to severe with numbness, weakness, muscle atrophy, and even difficulty moving the leg. The symptoms are usually only on one side, but they can be present bilaterally (down both legs) if central pressure (in the middle) is placed on the nerve tissues.

Treatment of sciatica often requires finding out what's causing the problem. A disc protruding out of the disc space and compressing or irritating the spinal nerve has a very different treatment approach than a tumor pressing on the nerve.

The diagnosis begins with the patient's report of his or her symptoms, what brought them on (if anything), what makes the pain better or worse, and so on. This can help the examiner pinpoint the cause of the problem. Special clinical tests can also be conducted. For example, if the clinician suspects involvement of the sciatic nerve, the straight leg raise test is done.

In this test, the patient sits or lies down on his or her back (supine position). In the sitting position, the examiner passively straightens the patient's leg. In the supine position, the straight leg is passively lifted. Rrepoducing the symptoms with these movements is usually a positive test indicating the presence of sciatica.

A positive straight-leg raise doesn't tell us what's causing the problem. Further testing is needed for a more definitive diagnosis. X-rays or more advanced imaging with MRI or CT scans may be ordered.