Straight leg raise (SLR) is a test to evaluate if a nerve root is stimulated at the place where it emerges from the spine. The extent to which the patient feels pain during the test, provides an indication of the cause of this pain.
The straight leg raise is usually performed in people with low back pain. It is intended to distinguish between lumbago (back pain without root stimulation) and sciatica (back pain with root stimulation, often as a result of spinal disc herniation).
In this examination, the nerve is slightly pulled. If this causes severe pain, the nerve root is likely to be more or less pinched. The cause is often a herniated spinal disc. The test is not one hundred percent reliable, but usually rapidly provides a good evaluation.
The test is conducted as follows: the patient is lying on his back with stretched legs. The investigator slowly lifts one leg first, than the other leg in stretched position. As a result, the sciatic nerve and its nerve roots are slightly pulled. From a specific angle of lifting the stretched leg, the patient may feel radiating pain in this leg. This makes further lifting very unpleasant. In this case, the straight leg raise is positive. The doctor measures or estimates the angle and writes it down, together with which leg is involved.
The straight leg raise is negative when the doctor can lift the stretched leg up to ninety degrees, without the patient feeling pain.