Straight-leg tests are done to help find the reason for low back and leg pain. To do this test, you lie on your back with
both legs straight. Your health professional raises one of your legs upward,
keeping the knee straight.
Your doctor may do this test on each leg. The test stretches the sciatic nerve that runs down the back of your leg and the nerve roots that lead to it.
If you have pain down the back of your leg below
the knee when your affected leg is raised, the test is positive
(abnormal). It means that one or more of the nerve roots leading to your sciatic nerve may be compressed or irritated.
If doing this test on the unaffected leg causes pain in
the affected leg, it helps to confirm that one of these nerve roots is compressed or irritated.
Compression or irritation of the nerve roots leading to the sciatic nerve can have several causes, but the most common is a herniated disc at the lowest part of your back.