You’re in the middle of a lumbar evaluation, and the patient reports sharp pain shooting down the back of their leg when you lift their straightened leg. That’s the classic response you’re looking for with the Straight Leg Raise Test (SLR)—a cornerstone special test for nerve root irritation and a must-know for any clinician tackling low back pain.
What is Straight Leg Raise Test?
The Straight Leg Raise Test (also called Lasègue’s sign) is a passive neurodynamic test used to assess mechanosensitivity of the sciatic nerve and its nerve roots, most commonly L5 and S1. With the patient lying supine, you lift the symptomatic leg with the knee extended while keeping the ankle neutral. The test is considered positive when symptoms—especially radicular pain below the knee—are reproduced between 30 and 70 degrees of hip flexion.
Why Straight Leg Raise Test Matters in Physical Therapy Practice
This test is a critical screening tool for lumbar disc herniation and nerve root compression. A positive SLR influences your entire Plan of Care: it highlights the need for neural mobilization, movement modification, and education on positions that reduce intradiscal pressure. It also helps you identify red flags and communicate clearly with referring providers about the likelihood of nerve involvement.
What You’ll See in the Clinic
Patients often present with unilateral leg pain, numbness, or tingling that worsens with sitting or bending forward. You’ll reproduce their familiar radiating pain when performing the SLR. You might also notice subtle guarding or a posterior pelvic tilt as the leg is lifted.
“SLR on the right reproduces patient’s posterior thigh and calf pain at 45 degrees with positive sensitization on ankle dorsiflexion. Left SLR is limited by hamstring tightness without distal symptoms. I will initiate nerve glides and teach positional lumbar flexion relief strategies.”
Common Pitfall & Pro Tip
⚠️ Pitfall: Calling a positive test simply because you feel hamstring tightness. Hamstring tightness is felt in the posterior thigh, not below the knee, and doesn’t reproduce true radicular symptoms.
💡 Pro Tip: Add ankle dorsiflexion at the end of the available range to sensitize the nerve root. If this intensifies the distal pain, you’ve got a much stronger positive SLR.
Memory Aid for Straight Leg Raise Test
Think “Nerve before muscle”: When lifting the leg, stop when the patient mentions symptoms that travel past the knee—that pain is the nerve’s way of saying “enough.” For values, remember “30 to 70, nerve is plenty; above 70, hammy’s heavy.”
NPTE Connection
This appears frequently in questions about differentiating nerve root compression from hamstring tightness, and in scenarios describing positive findings in lumbar disc herniation.
Related Physical Therapy Concepts
The SLR pairs well with Crossed Straight Leg Raise (more specific but less sensitive for disc herniation) and the Slump Test for additional neural tension assessment. Understanding this test also connects to lumbar centralization concepts and the treatment of radiculopathy through directional preference and neural mobilization.
Quick Reference
✓ Positive test: Reproduction of radiating pain below knee at 30–70° hip flexion ✓ Priority level: High—guides diagnosis and neural-based treatment approach ✓ PT Interventions/Considerations: • Differentiate radicular pain from hamstring tightness • Use ankle dorsiflexion as sensitizer • Implement neural glides or tensioners • Educate on posture and avoidance of aggravating positions • Reassess after manual therapy or movement intervention
Bottom line: The Straight Leg Raise Test is more than a special test—it’s a direct window into how irritable your patient’s nervous system really is.