The Straight Leg Raise (SLR), a test often used to tension the sciatic nerve, is well known for its ability to rule in or rule out lumbar nerve root pathology (radiculopathy) that may be manifesting along the sciatic nerve trajectory. This often presents as leg pain, numbness, and/or tingling of the lower extremity.
To perform a SLR, with the patient supine, the examiner raises the leg into passive hip flexion while maintaining the knee in extension.
So how is a negative or positive SLR test defined? The criteria can vary from source to source. Some literature states that the absence of leg pain and/or paresthesia constitutes a negative test while the presence of the above would be a positive test. Other literature suggests that raising the leg into more than 70 degrees of hip flexion defines a negative test. The inability to reach 70 degrees of hip flexion in combination with lower extremity symptoms would define a positive test result. With variable criteria there is more room for interpretation which can affect overall test reliability. Simply stated, you and I may not come to the same conclusions when using this test on the same patient. This is known as inter-rater reliability.
Reproduction of symptoms along a dermatomal distribution has moderately good inter-rater reliability while leg pain does not (Vrooman, et al. 2000). A range of hip flexion below 70 degrees has not been universally agreed upon and can vary in patients that are hypermobile or who may be experiencing mild residual symptoms.
Several issues with SLR reliability have been identified. For example, posterior thigh discomfort from hamstring tension, is often misinterpreted as a positive SLR. A lack of standardization in testing position is another issue that commonly occurs. Performing a SLR with the head elevated on pillows, not locking out the knee, allowing the lower extremity to veer into slight abduction/adduction, and allowing the hip to medial/lateral rotate are some examples that can potentially skew your findings leading to false positives or negatives.
The SLR has been highlighted in the literature for its specificity and by standing the test of time for ruling in lumbar radicular pathology. Unfortunately, the studies that draw these conclusions, are mainly performed in surgical clinics which biases the patient populations being studied. This does not allow much room for false positives. As acupuncturists, a surgical patient population doesn’t necessarily reflect the patient population that most practitioners are encountering on the day to day. In fact, a Cochrane systematic review in 2010, looked at the accuracy of a SLR among clinics who serve the general population. The findings did not support the use of a SLR to determine nerve root pathology and there was not a clinically relevant shift in post-test probability.
Is a SLR still useful or should we just skip this test altogether? Yes and no. A SLR is still useful and worth the time to perform although we need to alter how we define a positive test. A systematic review by Scaia, et al. in 2012 suggests that asymmetry of motion from side to side, using neural tensioning maneuvers, and reproducing the patient’s exact symptoms could make a SLR more clinically useful. As such, I have summarized this as the ABC’s of a Straight Leg Raise for ease of memory and application.
A - asymmetry with less range when compared to the asymptomatic side
B - Bragard’s Test (a common neural tensioning maneuver used in combination with a SLR)
C - concordant sign (reproduces the patient‘s exact symptoms. More reliable when symptoms follow dermatomal distributions rather than just general pain and/or paresthesia)
Why should this matter to you? Regardless of acupuncture style, knowing the origin of pain and/or paresthesia assists in treatment specificity. For example, many patients with lumbar radiculopathy only present with leg pain. For these patients, lower extremity pain is a branch symptom manifesting from irritation more proximally at the nerve root. When searching for the root of a problem, using the ABC's of the SLR can help point you in the right direction.
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