A nurse is assessing a 58-year-old client who reports severe lower back pain radiating down the left leg. Which assessment finding would be most indicative of lumbar disc herniation?

The straight leg raise test is a specific diagnostic maneuver used to assess for lumbar disc herniation, particularly affecting the sciatic nerve.

The straight leg raise test (Lasègue test) is the most specific and sensitive clinical assessment method for diagnosing lumbar disc herniation, especially when the sciatic nerve is involved. This test is performed with the patient lying supine while the examiner slowly lifts the leg with the knee extended. It is considered positive if pain radiates from the lower back down the leg, particularly below the knee, at a hip flexion angle of 30–70 degrees.

Lumbar disc herniation is a condition in which the inner gel-like nucleus pulposus of the intervertebral disc protrudes through a tear in the outer annulus fibrosus, compressing the adjacent nerve root. It most commonly occurs at the L4-L5 and L5-S1 disc levels, where mechanical stress is increased. When the herniated disc material compresses the sciatic nerve or nerve root, characteristic symptoms appear, including sharp, burning pain radiating from the lower back to the posterior or lateral aspect of the leg, along with tingling, numbness, and muscle weakness.

The straight leg raise test reproduces these symptoms by stretching the sciatic nerve and increasing tension on the affected nerve root. Pain occurring during this test, especially below the knee, indicates nerve root compression and strongly suggests disc herniation. The sensitivity of the test increases when pain is reproduced at less than 60 degrees of hip flexion.

From a nursing perspective, accurate assessment of disc herniation is crucial for appropriate pain management, activity modification, and referral for further diagnostic imaging or specialist consultation. Nurses should also assess for red flag symptoms such as bowel or bladder dysfunction, which may indicate cauda equina syndrome requiring immediate surgical intervention.

Understanding the Clinical Presentation
The client’s report of severe lower back pain radiating down the left leg, described as sharp and burning, worsening with sitting or coughing, and accompanied by numbness in the foot, is a classic presentation of lumbar radiculopathy. When the nucleus pulposus of an intervertebral disc herniates, it can mechanically compress or chemically irritate a spinal nerve root. Activities that increase intrathecal pressure, such as coughing or sitting, exacerbate this compression, leading to a predictable increase in pain. The radiation of pain below the knee and into the foot suggests involvement of the L5 or S1 nerve root, which are the most common levels for lumbar disc herniation.

Analyzing the Answer Choices
The goal of the physical assessment is to reproduce the patient’s radicular symptoms by placing tension on the affected nerve root. A systematic review of the diagnostic accuracy of physical examination tests confirms that the straight leg raise (SLR) test is a primary pain provocation test for identifying lumbar disc herniation with nerve root involvement ^[1]. A positive test is defined by the reproduction of the patient’s characteristic leg pain, particularly when it radiates below the knee, at an angle between 30 and 70 degrees of hip flexion ^[1][2]. This finding demonstrates high sensitivity for disc herniation confirmed at surgery ^[2].

- Option 1 (Positive Babinski reflex and hyperactive deep tendon reflexes): These are upper motor neuron findings indicative of a lesion in the spinal cord or brain, not a unilateral nerve root compression. A herniated disc causing radiculopathy typically presents with lower motor neuron signs, such as diminished or absent deep tendon reflexes in the affected nerve root distribution.
- Option 2 (Muscle rigidity and fever with elevated white blood cell count): This cluster of findings is highly suggestive of an infectious or inflammatory process, such as a spinal epidural abscess or discitis. While these conditions can cause back pain, they are not the primary indicators of a mechanical disc herniation.
- Option 4 (Decreased range of motion in the cervical spine with neck stiffness): This finding localizes the pathology to the cervical spine, not the lumbar spine. Neck stiffness is a classic sign of meningeal irritation or cervical spine pathology and is not relevant to a lumbar disc assessment.

The Straight Leg Raise Test: Mechanism and Evidence
The SLR test is performed with the patient in a supine position. The examiner passively flexes the hip while keeping the knee extended. This maneuver stretches the sciatic nerve and the lumbosacral nerve roots (L4, L5, S1, S2, S3). In a patient with a herniated disc, the inflamed and compressed nerve root is sensitized to mechanical deformation. The test is considered positive if it reproduces the patient’s familiar radicular pain at an angle of leg elevation that is significantly lower than the normal range, typically between 30 and 70 degrees ^[1]. Pain occurring only in the back or hamstring tightness is not a true positive finding for nerve root compression.

The diagnostic value of this test is well-established. Research has shown a high correlation between a positive SLR test and the intraoperative finding of a disc herniation ^[2]. Furthermore, the degree of SLR restriction is related to the severity of the disc herniation and the patient’s pain-related symptoms, and it typically improves significantly following surgical decompression . A Cochrane review on the physical examination for lumbar radiculopathy also supports the use of the SLR test, often in combination with other neurological assessments, to identify patients likely to have a disc herniation .