The Straight Leg Raise (SLR) test is a standard physical examination maneuver used to evaluate the cause of lower back and leg discomfort. Its function is to assess the mobility and irritation of the lumbosacral nerve roots, particularly the sciatic nerve. When the sciatic nerve or its roots are compressed or inflamed, the tension applied during the test can reproduce the characteristic pain known as sciatica. The SLR test provides immediate information regarding whether symptoms are likely rooted in nerve compression, most commonly due to a herniated disc in the lumbar spine.
Performing the Straight Leg Raise Test
To perform the SLR test, the individual should lie flat on their back (supine) with both legs fully extended. The person must remain relaxed throughout the procedure, as the test is performed passively by the examiner. The knee of the leg being tested must be kept completely straight to ensure maximum tension is applied to the sciatic nerve pathway.
The examiner slowly raises the individual’s leg upward, flexing the hip joint. This movement continues until the individual first reports feeling pain or significant tightness along the back of the leg or in the back. Observation of the exact point at which symptoms begin is an important step in the process. The angle between the leg and the examining surface at the onset of pain must be noted, as this measurement is central to interpreting the result.
A sensitizing maneuver can be included to confirm if the pain originates from the nervous system rather than muscle tension. Once discomfort is reached, the examiner slightly lowers the leg until the pain subsides, then sharply flexes the foot upward (dorsiflexion). If this action immediately reproduces the familiar radiating pain, it suggests irritation of the sciatic nerve or its roots. The test should be terminated immediately if the pain becomes severe or if the individual experiences a sudden onset of weakness or numbness.
Understanding Positive and Negative Findings
A positive SLR test is defined by the reproduction of the individual’s familiar radiating leg pain (radiculopathy), which travels below the knee. This reproduction of symptoms typically occurs between 30 and 70 degrees of hip flexion. Pain felt in this angle range is suggestive of mechanical compression or inflammation of a lumbar nerve root, often caused by a herniated disc at the L4-L5 or L5-S1 spinal levels.
A negative test is characterized by either no pain being felt during the entire range of motion or by pain limited to the hamstring muscle or the lower back. If pain only begins after the leg has been raised beyond 70 degrees, it is attributable to hamstring tightness or stiffness in the hip or sacroiliac joint, not nerve root irritation. Pain felt only in the back, without traveling down the leg, also does not constitute a positive test for sciatica.
An important variation is the Crossed Straight Leg Raise (CSLR) test, performed by raising the unaffected leg. The test is considered positive if this action causes radiating pain in the opposite affected leg. Although the CSLR is less sensitive than the standard SLR test, it is highly specific. A positive CSLR test is a strong indicator of a large, centrally located disc herniation causing significant nerve root tension.
Safety Precautions and Limitations
The Straight Leg Raise test is a valuable screening tool but is not a standalone diagnostic measure. Only a qualified healthcare professional can use the test results alongside a full medical history and other physical findings to establish a definitive diagnosis. The test has high sensitivity, making it effective for ruling out nerve compression if the result is negative. However, its low specificity means a positive result alone does not confirm a diagnosis of a disc herniation.
Certain situations caution against performing the SLR test or require care, especially outside of a clinical setting. The test should not be attempted on individuals who have recently experienced trauma, have suspected pelvic or leg fractures, or are dealing with severe, unrelenting pain. If the leg cannot be raised even a short distance due to immediate, excruciating pain, the test should be abandoned immediately.
Individuals attempting a modified version of the test should stop immediately and seek professional medical attention if the maneuver causes an increase in severe pain or new neurological symptoms. These symptoms include a sudden loss of feeling, increased numbness, or the development of muscle weakness, such as foot drop. These signs may indicate rapidly worsening nerve compression that requires urgent medical evaluation.