What is the significance and management of a positive Lasegue (straight leg raise test) sign in a patient?

Lasegue Sign: Clinical Significance and Management

What is the Lasegue Sign?

The Lasegue sign (straight leg raise test) is a highly sensitive (91%) but poorly specific (26%) indicator of lumbar disc herniation causing nerve root compression—a positive test strongly suggests sciatica and warrants conservative management initially, with imaging reserved for red flags or persistent symptoms beyond 4-6 weeks. 1

The test is positive when radiating leg pain below the knee is reproduced during passive leg elevation between 30-70 degrees with the knee extended. 2 This maneuver stretches the sciatic nerve to elicit symptoms of nerve root tension. 3

Diagnostic Performance and Interpretation

Standard SLR Test

• Sensitivity: 91% (misses only 9% of true disc herniations) 1
• Specificity: 26% (many false positives occur) 1
• The test's sensitivity decreases significantly with age, dropping below 50% in patients over 60 years old 1

Crossed SLR Test (More Specific Variant)

• Sensitivity: 29% but Specificity: 88% 1
• Pain is produced when raising the unaffected leg 1
• A positive crossed SLR strongly indicates disc herniation and is highly specific 2

Critical Caveat

A negative Lasegue sign does NOT rule out lumbar disc herniation—the diagnosis of sciatica is based on the clinical pattern of radicular pain, dermatomal sensory changes, and motor weakness in a nerve root distribution, even without a positive SLR. 1

Comprehensive Neurological Examination

When the Lasegue sign is positive, perform a focused neurological assessment targeting specific nerve roots: 1

• L4 nerve root: Knee strength and knee reflexes
• L5 nerve root: Great toe dorsiflexion and foot dorsiflexion strength
• S1 nerve root: Foot plantarflexion and ankle reflexes
• Sensory distribution: Map dermatomal patterns corresponding to affected nerve roots

Red Flag Assessment (Requires Immediate Action)

Immediately obtain MRI if any of the following are present: 2, 3

• Severe or progressive neurological deficits
• Cauda equina syndrome (urinary retention has 90% sensitivity) 2
• Significant risk factors for cancer, vertebral infection, or compression fracture 3
• Progressive motor weakness

Initial Management for Positive Lasegue Sign Without Red Flags

First-Line Conservative Treatment (4-6 Week Trial)

Pharmacological Management: 2

• NSAIDs for pain relief and anti-inflammatory effects
• Muscle relaxants for associated muscle spasm
• Short-term oral corticosteroids may be considered for severe radicular pain

Non-Pharmacological Interventions: 2

• Spinal manipulation by appropriately trained providers (shows small to moderate short-term benefits for acute sciatica)
• Activity modification: Avoid positions that increase nerve tension while maintaining tolerable activity levels
• Exercise therapy, acupuncture, massage therapy, and cognitive-behavioral therapy for chronic sciatica

Positioning Recommendations

• Avoid positions that increase nerve tension and pain 2
• If spinal injury is suspected, do not move the patient unless necessary for safety, using proper spine stabilization techniques 2

Imaging Strategy

Delayed Imaging (After 4-6 Weeks) is Appropriate For: 2, 3

• Persistent sciatica without improvement despite conservative management
• Consideration of surgical intervention
• Persistent positive SLR test

MRI is the preferred imaging modality when indicated. 3

When to Refer for Specialist Evaluation

Refer patients with: 2, 3

• Persistent symptoms after 4-6 weeks of conservative treatment
• Progressive neurological deficits
• Persistent positive SLR test despite conservative management

Surgical Consideration Criteria: 2, 3

• Persistent radicular symptoms
• Significant functional limitations
• Concordant imaging findings showing disc herniation

Important Clinical Pitfalls

Psychosocial factors are stronger predictors of low back pain outcomes than physical examination findings alone—assess for depression, anxiety, catastrophizing, and work-related stress. 2, 3

The high incidence of asymptomatic disc herniations on MRI (false-positive imaging findings) means the SLR test must be interpreted in conjunction with clinical findings, not imaging alone. 1, 4

Test performance varies by herniation characteristics: 5

• Most sensitive and specific for lateral herniations at L4-5
• Decreased sensitivity for median and paramedian herniations
• Decreased specificity for L3-4, migrated, and sequestered disc herniations

Prognostic Value

A positive Lasegue sign assessed 3 months after disc surgery predicts poor functional outcomes, increased risk of not returning to work, higher reoperation rates, and diminished quality of life at 24-36 months. 6