The straight leg raise test has been around since 1880. It is used as a way to look for back pain caused by the disc pressing against the spinal nerves. The test is done with the patient lying on his or her back. The examiner lifts one of the patient’s legs without help from the patient. The leg is kept straight at the knee.
This is called a passive straight leg raise (PSLR). The test is stopped when the patient feels back or leg pain. This is considered by some examiners to be a positive PSLR. If there isn’t any pain or symptoms during this test, it is considered a negative PSLR.
The basic PSLR test can be done with slightly different variations. Sometimes ankle motion (up or down) is added. The patient may be asked to lift the head and bend the neck forward. Other testers turn or rotate the hip in. Another variation elevates the leg with the knee bent. Symptoms of back or leg pain occur only when the knee is straightened. This is known as the Lasègue’s sign or Lasègue’s test.
Just exactly what a positive test tells the examiner is questionable. Some studies show that the PSLR position pulls on the sciatic nerve, causing pain. Others suggest that the test shows inflammation of the spinal nerves as they leave the spinal cord and travel down the spine. Some use the test to show that a disc is pressing on the spinal nerve.
A worldwide review of studies on the PSLR test was done by a group of doctors in Ireland. Studies from 1989 to 2000 were included. Researchers wanted to know what changes have occurred with this test since its use began in 1880. They also looked to see how the test is used and what its results mean.
They found that the basic test remains unchanged after more than 100 years of use. However, there are as many ways to view the results as there are examiners. In other words, a positive test means something different to nearly each person using the test.
One use the PSLR has is to predict results after disc surgery. A positive PSLR four months after surgery is a sign of poor recovery. A negative PSLR (no pain or symptoms when the straight leg is elevated) predicts an excellent outcome.
More research is needed to clear up other uses and meanings of this test. Differences according to age and gender remain unknown. The effect of psychosocial factors is also unknown. A negative PSLR may actually give more helpful information than a positive result.