Lumbar Radiculopathy: Straight Leg Raise (SLR), Well-Leg Cross-SLR, and Nerve Tension Diagnostics
In short
The Straight Leg Raise test provides high sensitivity for lumbar disc herniation, while a positive Crossed SLR achieves 90% specificity for large axillary disc fragments.
In this guide (4 sections)
Neurodynamics and Mechanical Strain on the Sciatic Nerve Roots
Lumbar Radiculopathy (commonly termed sciatica) is characterized by radiating lancinating pain, paresthesias, and neurological deficits following a discrete dermatomal and myotomal distribution in the lower extremity. Overwhelmingly caused by posterolateral herniation of the nucleus pulposus at L4-L5 (compressing the L5 nerve root) or L5-S1 (compressing the S1 root), the pathology features both mechanical compression and intense chemical radiculitis driven by pro-inflammatory disc cytokines (TNF-alpha, IL-6).
Under physiological conditions, lower extremity movement requires substantial neural excursion: the sciatic nerve and its roots slide 2 to 8 mm within the intervertebral foramen. When a disc herniation tethers or compresses the root, passive hip flexion and knee extension generate rapid, painful tensile traction across the inflamed neural segment.
The Straight Leg Raise (SLR) vs Crossed SLR Diagnostic Matrix
| Diagnostic Test | Patient Examination Maneuver | Positive Pathological Finding | Diagnostic Sensitivity & Specificity | |
|---|---|---|---|---|
| Straight Leg Raise (SLR / Lasegue) | Passive leg elevation with knee fully extended and foot relaxed | Shooting dermatomal pain radiating below the knee between 30 and 70 deg | HIGH Sensitivity (~91%); MODERATE Specificity (~52%) | |
| Crossed SLR (Well-Leg Raise) | Passively raise the UNINJURED (healthy) leg into straight leg raise | Reproduction of shooting radicular pain down the SICK / AFFECTED leg | LOW Sensitivity (~29%); EXCEPTIONAL Specificity (~90%) | |
| Braggard's Sign (Sensitizing) | Lower leg to just below pain angle; add passive ankle dorsiflexion | Immediate reproduction of sharp electric radicular pain | Differentiates true neural tension from tight hamstring muscle pull | |
| Bowstring Sign (Cram Test) | Flex knee slightly to relieve pain; apply deep thumb pressure into popliteal fossa | Sharp radicular pain reappears on direct sciatic nerve compression | Confirms peripheral neural mechanosensitivity | |
| Angle Interpretation Window | < 30 deg: hip pathology / malingering; 30-70 deg: true disc root tension; > 70 deg: hamstrings | 30 to 70 degrees is the true physiological neural tension arc | Pain past 70 degrees without Braggard is simple hamstring tightness |
Standardized Clinical Physiotherapy and Gliding Protocols
- The Meaning of a Positive Crossed (Well-Leg) SLR: Recognize that a positive Crossed SLR is a major diagnostic red flag; pulling the unaffected nerve root tight pulls the dural sac caudad, wedging a large medial or axillary disc fragment into the affected nerve root; this finding correlates with large herniations requiring surgical referral.
- Sciatic Nerve Gliding (Sliders) Over Static Tensioning: Never perform aggressive static hamstring stretches in acute sciatica; stretching an inflamed, ischemic nerve root exacerbates axonal damage; prescribe gentle sciatic sliders (extending the knee while simultaneously extending the neck and plantarflecting the ankle).
- Prone Press-Ups for Centralization Screening: Screen the patient for directional preference using McKenzie prone press-ups; if repeated extension centralizes radiating calf pain back into the buttock or lower back, prescribe 10 press-ups every 2 hours.
Frequently Asked Questions
What is the Straight Leg Raise test for sciatica?
In the Straight Leg Raise test, you lie on your back while the physiotherapist gently lifts your straight leg up toward the ceiling. If raising your leg between 30 and 70 degrees triggers shooting electric shocks or pain down past your knee, it proves a bulging disc is pinching your sciatic nerve.
What does it mean if lifting your good leg causes pain down your bad leg?
This is called the Crossed Straight Leg Raise test. Lifting your pain-free leg pulls on the main spinal cord sheath, which yanks the pinched nerve on your bad side against a large bulging disc. A positive test is a strong sign of a large disc herniation.
Why shouldn't you aggressively stretch your hamstrings when you have sciatica?
When you have sciatica, that tight feeling behind your thigh is an inflamed, irritated nerve, not a short muscle. Aggressively stretching your leg pulls the angry nerve like a rubber band, making your pain and nerve swelling twice as bad.
Related condition guides
Related recovery guides & articles
BookPhysio.in Editorial Team
The BookPhysio.in editorial team writes and maintains this content, checking it against reliable clinical sources. Content follows our medical review policy: general information only, and no page claims a clinical review until a named registered physiotherapist has signed it off.
Read our medical review policy