The straight leg raise (SLR) test checks for irritation or compression of the sciatic nerve and the nerve roots in your lower back. It’s one of the most common physical exam techniques used to evaluate whether a herniated disc is pressing on a nerve, particularly at the L4 through S1 levels of the lumbar spine. If you’ve gone to a doctor with leg pain, numbness, or shooting pain down the back of your thigh, there’s a good chance this test was part of your exam.
How the Test Works
You lie flat on your back while a clinician slowly lifts one of your legs by the ankle, keeping your knee straight. As the leg rises, it creates increasing tension on the sciatic nerve and pulls on the nerve roots where they exit the lower spine. The clinician watches for your reaction and notes the exact angle at which pain appears.
The critical window is between 30 and 70 degrees of hip flexion. Pain that shoots down your leg within this range strongly suggests a lumbar disc herniation compressing a nerve root. Pain that only appears beyond 70 degrees is more likely coming from tight hamstrings or the hip joint itself, not from a pinched nerve. And discomfort below 30 degrees, before the nerve is under meaningful tension, may point to other causes like joint inflammation or extreme sensitivity in the area.
What a Positive Result Means
A positive SLR test means that lifting the leg reproduced or worsened neurological symptoms: sharp, shooting, or electrical pain traveling down the leg, often following a specific path into the calf or foot. This pattern points to a nerve root being irritated, most commonly by a bulging or herniated disc in the lower lumbar spine.
Disc herniation is the most common cause, but it’s not the only one. Facet joint cysts (small fluid-filled sacs near the spinal joints), inflammatory conditions affecting the nerve roots, and rarely, spinal tumors can all produce a positive result. The test identifies nerve irritation, not the specific cause of it. That’s why imaging like an MRI is typically needed to confirm what’s actually going on.
Accuracy of the Test
The SLR test is better at catching nerve compression than it is at ruling out other causes of your pain. One study of 112 patients found a sensitivity of 77% and a specificity of 81%, meaning it correctly identified about three-quarters of people with confirmed nerve root compression and correctly cleared about four in five people without it. Those numbers are solid for a bedside exam, but they also mean the test misses some cases and occasionally flags problems that aren’t there.
A large systematic review found the numbers can swing widely depending on the population being tested, with sensitivity ranging from 52% to 91% and specificity dropping as low as 26% in some studies. In older adults over 60, sensitivity drops significantly to around 33%, likely because age-related spinal changes make the test less reliable. Tight muscles, anxiety during the exam, and existing hip or knee problems can also influence results.
The Crossed Straight Leg Raise
Sometimes a clinician will perform the test on your pain-free leg instead. If lifting the opposite leg reproduces symptoms on the affected side, that’s called a crossed straight leg raise, and it carries more diagnostic weight. This variation is associated with disc herniation in roughly 97% of patients who test positive for it, because it takes a larger, more centrally located disc bulge to irritate a nerve root from the opposite side.
The trade-off is that this crossed version misses most cases. It has low sensitivity, meaning many people with real disc herniations will test negative on it. But when it is positive, it’s a strong signal that something significant is going on. It’s worth noting that reliability between different examiners is inconsistent, so results can vary depending on who performs the test.
Seated vs. Lying Down Versions
Some clinicians perform the test while you’re sitting on the edge of an exam table, straightening your knee to create the same nerve tension. This seated version is useful as a consistency check. If you test positive lying down but show no pain when the same stretch is applied while seated, the results may be less reliable. One study found the seated version had a sensitivity of about 49% and specificity of 69% for herniations at the L5-S1 level, making it less accurate than the supine version but still useful as a supplementary check.
Modifications That Add Precision
When the basic test produces an ambiguous result, your clinician may add a small modification: dorsiflexing your ankle (pulling your toes toward your shin) at the point where pain begins. This is known as Bragard’s sign, and it puts additional stretch on the sciatic nerve. If the ankle movement increases your leg pain, it strengthens the case that the pain is genuinely coming from nerve tension rather than from muscles or joints. This modification has a sensitivity of about 69% and specificity of 76%, and it performs best in people whose symptoms started within the past three weeks.
How It Compares to the Slump Test
The slump test is another nerve tension exam, but it involves sitting hunched forward with your chin tucked to your chest while the knee is straightened. This position loads the entire spinal cord and nerve system more aggressively than the SLR. A comparative study found the slump test detected disc herniations at the L4-L5 level in 93% of confirmed cases, compared to 70% for the straight leg raise. The slump test is generally considered more sensitive, though the SLR remains the more widely used screening tool because of its simplicity and decades of clinical validation.
What Happens After a Positive Test
A positive straight leg raise is a starting point, not a final diagnosis. It tells your clinician that nerve irritation is likely involved in your symptoms, which narrows down the possible causes and helps guide next steps. For most people, that means imaging (usually an MRI) to visualize the disc and nerve root directly, along with a neurological exam checking reflexes, muscle strength, and sensation in your legs and feet.
If your symptoms are mild and recent, your clinician may recommend a period of conservative management first, since many disc herniations improve on their own within weeks to months. The SLR test is also useful for tracking progress over time. As a herniation shrinks or inflammation settles, the angle at which pain appears during the test typically increases, meaning the nerve is under less pressure. A test that was positive at 40 degrees improving to pain-free at 70 degrees is a concrete sign that things are moving in the right direction.