The Straight Leg Raise (SLR) test can be used to determine if patient has true sciatica.
The patient lies supine with one leg either straight or flexed at the knee with the sole of the foot flat on the stretcher.
The other (affected) leg is kept straight and raised up by the examiner.
The test is positive when raising the leg between 30 to 70 degrees causes pain to occur and radiate down the leg to at least below the knee, and often all the way down to the great toe (sensitivity 91%, specificity 26%).
Sensitivity may improve with dorsi-flexion of the foot while the leg is elevated.
The following do NOT indicate a positive test: pain of lower back only, without radiation to below knee; overtly excessive pain behavior; patient contraction of antagonist muscles that limit examiner's testing; tightness of buttock and hamstring muscles; nonspecific complaints.
The SLR test can also be performed with the patient in a sitting position, by stretching the sciatic nerve by extending the knee; the test is positive if pain radiates to below the knee.