I am a physical therapy student getting ready to put on an in-service for the clinic where I am training. I've chosen to do a case presentation on low back pain with radiculopathy. I'm finding many opinions about the use of the straight-leg raise test for patients with back pain. No one seems to agree on the best way to do this test. What can you tell me?
The passive straight-leg raise (SLR) test has been a standard testing tool used by doctors, physical therapists, and chiropractors for many years. The test is done with the patient lying supine (on his or her back). The examiner lifts one leg (knee straight) to an angle between 30 and 70 degrees.
If the patient experiences painful back or leg symptoms (on either side), it's considered a positive test for compression of the sciatic nerve called sciatica. The probable cause is disc protrusion or herniation. But bone spur, tumor, or infection can also cause a positive straight-leg raise test.
The clinician relies on patient history and other clinical tests to find out more specifically what's going on. There are other conditions that can produce or mimic sciatica such as shingles, diabetic neuropathy, abscess of the psoas muscle, and peripheral vascular disease.
As you have discovered, there isn't agreement on the definition of a positive straight-leg raise test. There isn't even a consensus of which structures are being stretched at each point in the range-of-motion.
Some experts feel that tension is placed on the nerve at 30 degrees of hip flexion. Others believe a positive straight-leg raise can be a protective reflex of the hamstring muscles. At least one study has shown that the nerve, nerve root, and dura (covering of the spinal cord) can be restricted causing a positive test. Stretching or tractioning the nerve over a herniated disc can (but doesn't always) cause a positive straight-leg raise.