What is a positive Straight Leg Raise (SLR) test indicative of?

From the Guidelines

A positive straight leg raising test is indicative of lumbar disc herniation, specifically at the L4/L5 and L5/S1 levels, with a relatively high sensitivity of 91% [ 1 ]. This test is performed by having the patient lie supine while the examiner slowly raises the patient's straightened leg, and pain radiating down the leg in a dermatomal distribution at an angle between 30 and 70 degrees constitutes a positive test. The mechanism involves stretching of the sciatic nerve and its nerve roots, which causes pain when there is compression or inflammation, as noted in the study published in the Annals of Internal Medicine [ 1 ]. Key points to consider when interpreting the results of the straight leg raising test include:

• The test has a modest specificity of 26% for diagnosing herniated disc [ 1 ]
• The crossed straight-leg-raise test is more specific but less sensitive for diagnosing herniated disc [ 1 ]
• A focused examination that includes straight-leg-raise testing and a neurologic examination should be done to assess the presence and severity of nerve root dysfunction [ 1 ]
• The test should be interpreted alongside other neurological findings and imaging studies for a complete diagnosis of radiculopathy or disc pathology.

From the Research

Positive Straight Leg Raising Test Indications

• A positive straight leg raising test is indicative of lumbar disc herniation (LDH) 2, 3, 4
• The test is used to diagnose sciatica and radicular leg pain due to LDH 2, 3, 5
• A positive test result is associated with pain at rest, pain at night, pain upon coughing, and reduction of walking capacity 4
• The test has a strong correlation with various parameters that signify the pain level of the patient 4

Factors Affecting Test Results

• Age: the rate of positive test results declines with increasing age 2, 3
• Sex: men have a higher chance of positive test results than women 2
• Disk level: the test results are affected by the level of disk herniation 2
• Periradicular adhesive tissue: can limit nerve root movement and cause transient conduction disturbances 5

Test Accuracy and Reliability

• The test has low accuracy in diagnosing LDH compared to MRI results 3
• The discriminative power of the test decreases with increasing age 3
• A positive test result postoperatively correlates with inferior surgical outcome 4