From the Guidelines
A positive straight leg sign represents nerve root irritation or compression, typically in the lower back, with a relatively high sensitivity of 91% for diagnosing herniated disc. This test is performed by having a patient lie flat on their back while the examiner slowly raises the patient's straightened leg. If the patient experiences radiating pain down the leg (sciatica) when the leg is raised between 30 and 70 degrees, the test is considered positive, as noted in the study by 1. This finding commonly suggests lumbar disc herniation pressing on nerve roots, particularly affecting the L4, L5, or S1 nerve roots. The pain occurs because stretching the sciatic nerve during leg elevation increases tension on the irritated nerve root. Some key points to consider when interpreting the results of a straight leg sign include:
- The test has a modest specificity of 26% for diagnosing herniated disc, as reported in the study by 1
- The crossed straight-leg-raise test is more specific but less sensitive for diagnosing herniated disc, with a specificity of 88% and a sensitivity of 29%, as noted in the study by 1
- The test is valuable in evaluating patients with low back pain and suspected radiculopathy, helping clinicians determine if nerve compression is contributing to the patient's symptoms and potentially guiding treatment decisions, including physical therapy, medication management, or in some cases, surgical intervention. It is essential to consider the patient's overall clinical presentation, including their medical history, physical examination findings, and results of any diagnostic tests, when interpreting the results of a straight leg sign, as emphasized in the study by 1.
From the Research
Positive Straight Leg Sign Representation
- A positive straight leg sign is typically indicative of a herniated lumbar disc, as it suggests that the patient is experiencing pain or discomfort when the leg is raised to a certain angle, usually between 30 to 60 degrees 2, 3.
- The sign is considered positive when the patient experiences pain or discomfort in the lower back, buttock, or leg when the straight leg is raised, and this pain is relieved when the leg is lowered 4, 5.
- A positive straight leg sign can also be correlated with the severity of symptoms in lumbar disc herniation, with more restricted positive tests (i.e., pain at lower angles) indicating more severe symptoms 5.
- The presence of a positive straight leg sign postoperatively can be an indicator of an unfavorable surgical outcome, with patients experiencing persistent pain or discomfort after surgery 4, 5.
- However, it's worth noting that a positive straight leg sign is not exclusive to herniated lumbar discs and can be present in other conditions, such as sciatica or lower back pain 3.
- Additionally, the absence of a positive straight leg sign does not necessarily rule out the presence of a herniated lumbar disc, as some patients may not exhibit this sign despite having a disc herniation 2.