A straight leg raise test is performed by having the patient lie flat on a bed. With the leg straight, the patient should then raise their foot off the bed and hold it in the air. People should be able to hold the leg straight up with the heel elevated off an examination bed. In addition, light resistance is often applied by the examiner to test strength.

In addition, physicians can perform a similar test by lifting the heel up as high as possible, and then point the toes towards the patient's head. This stretches the sciatic nerve and can help diagnose conditions of nerve irritation called radiculopathy.

Testing the Extensor Mechanism

The straight leg raise tests several aspects of strength and stability of the extremity. Most often, the straight leg raise test is used to assess the function of the quadriceps muscle and its attachment to the shin bone. A disruption of the quadriceps tendon, patella, or patellar tendon can lead to the inability to perform a straight leg raise.

When someone has a condition such as a torn quadriceps tendon or a patella fracture, they are generally unable to perform this maneuver. Because of the disruption of the extensor mechanism, despite the patient's effort to lift the leg, there is nothing to pull against, and therefore they aren't able to perform this function. A straight leg raise test is the key diagnostic test to assess for these conditions.

Testing Nerve Irritation

The straight leg test can be altered to test nerve function rather than muscle and tendon function. The sciatic nerve exits from the lumbar spine and passes behind the hip and down the back of the lower extremity. Conditions that cause nerve irritation, including spinal stenosis, disc herniations, and sciatica, can also be tested with a variation of the straight leg raise maneuver.

Rather than having the patient attempt to lift the extremity, the examiner lifts the heel with the knee in a straight position. Once the heel has been lifted as high as possible, the examiner dorsiflexes the ankle (points the toes towards the patient's head). This stretches the nerve and can recreate symptoms of nerve pain going down the leg.

A positive test is when pain is recreated below the level of the knee. Feeling tightness in the hamstring muscle is not considered a positive test.

This type of test is called a tension sign and can be very helpful in determining the best treatment of a nerve condition.