Lumbar Disc Herniation Examination

Commonly Tested

Lumbar disc herniation examination requires systematic neurological assessment and provocative testing. Examiners expect you to perform the straight leg raise correctly, recognize the difference between L4, L5, and S1 radiculopathy, and always screen for cauda equina syndrome.

Exam day cheat sheet

Lumbar Disc Herniation Summary

Common Levels

L4-5 disc → L5 root (most common)
L5-S1 disc → S1 root (second most common)
L3-4 disc → L4 root (less common)

Key Tests

Straight leg raise (SLR) - 35-70° positive
Crossed SLR (highly specific)
Femoral stretch test (L3/L4)
Slump test (seated neural tension)

Root Differentiation

L4: Knee extension, patellar reflex, medial leg
L5: Great toe extension (EHL), lateral leg/dorsum foot
S1: Plantarflexion, ankle jerk, posterior calf/sole

Red Flags

Cauda equina: Saddle anesthesia, bladder/bowel, bilateral
Progressive motor weakness
Infection signs
Trauma with neurological deficit

Anatomy and Pathophysiology

Key Concepts

Lumbar Root Anatomy:

Roots exit BELOW their numbered vertebra
L4 root exits at L4-5 foramen
L5 root exits at L5-S1 foramen

Disc Herniation Patterns:

Posterolateral (most common): Compresses traversing root
- L4-5 posterolateral disc → L5 root
- L5-S1 posterolateral disc → S1 root
Far lateral/Foraminal: Compresses exiting root
- L4-5 far lateral disc → L4 root
Central: May affect multiple roots, cauda equina risk

Prevalence:

L5-S1: Most common level
L4-5: Second most common
Higher levels less common

Must Know

Cauda Equina Syndrome - Surgical Emergency: Screen EVERY patient with lumbar symptoms:

Saddle anesthesia (perineal numbness)
Bladder dysfunction (retention, incontinence)
Bowel dysfunction (incontinence)
Bilateral leg symptoms
Progressive motor weakness

If present → URGENT MRI and neurosurgical referral

Clinical Assessment

History Clues

Typical Disc Herniation:

Leg pain greater than back pain
Pain radiating below knee (sciatica)
Dermatomal distribution
Worse with sitting, flexion, Valsalva
Better with standing, extension, lying flat

Aggravating Factors:

Sitting (increases disc pressure)
Forward bending (flexion)
Coughing, sneezing, straining (Valsalva)

Relieving Factors:

Standing, walking
Lying flat
Extension

Provocative Tests

Special test

Straight Leg Raise (Lasègue Test)

Lumbosacral nerve root tension (L4-S1)

Technique

1Patient supine, leg straight
2Passively lift leg by heel, keeping knee extended
3Stop when patient reports pain
4Note angle at which pain occurs and distribution

Positive Sign

Reproduction of radicular leg pain between 35-70° of hip flexion

Indicates

Lumbosacral nerve root irritation (L4, L5, S1). Pain must radiate below knee to be significant

Diagnostic Accuracy

Sensitivity91%

Ability to detect true positives

Specificity26%

Ability to exclude false positives

Key Concept

SLR Interpretation:

Positive: Leg pain (below knee) between 35-70°
Negative: Back pain only, or leg pain above 70° or below 35°
Pain at less than 35° suggests malingering or sciatic nerve tumor
Pain at greater than 70° is likely hamstring tightness, not root tension
Must reproduce the patient's typical radicular symptoms

Special test

Crossed Straight Leg Raise (Contralateral SLR)

Confirm disc herniation

Technique

1Patient supine
2Raise the UNAFFECTED leg (straight)
3Observe if this produces pain in the AFFECTED leg

Positive Sign

Pain reproduced in the symptomatic leg when raising the asymptomatic leg

Indicates

Central or large disc herniation (highly specific for disc herniation)

Diagnostic Accuracy

Sensitivity29%

Ability to detect true positives

Specificity88%

Ability to exclude false positives

Special test

Bowstring Test (Popliteal Compression)

Confirm neural tension as cause of SLR pain

Technique

1Perform SLR to point of pain
2Lower leg slightly until pain resolves
3Flex knee slightly to take tension off
4Apply direct pressure to popliteal fossa (over sciatic nerve)

Positive Sign

Reproduction of radicular leg pain with popliteal pressure

Indicates

Sciatic nerve irritation (confirms neural origin of SLR pain)

Diagnostic Accuracy

Sensitivity71%

Ability to detect true positives

Specificity84%

Ability to exclude false positives

Special test

Femoral Stretch Test (Reverse Lasègue)

Upper lumbar root tension (L2, L3, L4)

Technique

1Patient prone
2Passively flex knee
3Extend hip (lift thigh off bed)

Positive Sign

Reproduction of anterior thigh pain (radicular pattern)

Indicates

L2, L3, or L4 nerve root irritation (stretches femoral nerve)

Diagnostic Accuracy

Sensitivity50%

Ability to detect true positives

Specificity75%

Ability to exclude false positives

Special test

Slump Test

Neural tension (sitting equivalent of SLR)

Technique

1Patient seated at edge of bed
2Slump forward (thoracic flexion)
3Flex neck (chin to chest)
4Extend knee
5Dorsiflex ankle

Positive Sign

Reproduction of radicular leg symptoms

Indicates

Neural tension. May be positive when SLR equivocal

Diagnostic Accuracy

Sensitivity84%

Ability to detect true positives

Specificity83%

Ability to exclude false positives

Neurological Examination by Root

motor: Knee extension (quadriceps), hip adduction
sensory: Medial leg (shin)
reflex: Patellar (knee jerk)
discLevel: L3-4

motor: Great toe extension (EHL), ankle dorsiflexion, hip abduction
sensory: Lateral leg, dorsum of foot, great toe
reflex: None reliable (medial hamstring)
discLevel: L4-5

motor: Ankle plantarflexion, hip extension, toe flexion
sensory: Posterior calf, lateral foot, sole
reflex: Ankle jerk (Achilles)
discLevel: L5-S1

root	motor	sensory	reflex	discLevel
L4	Knee extension (quadriceps), hip adduction	Medial leg (shin)	Patellar (knee jerk)	L3-4
L5	Great toe extension (EHL), ankle dorsiflexion, hip abduction	Lateral leg, dorsum of foot, great toe	None reliable (medial hamstring)	L4-5
S1	Ankle plantarflexion, hip extension, toe flexion	Posterior calf, lateral foot, sole	Ankle jerk (Achilles)	L5-S1

Key Concept

Quick Root Differentiation:

L4: "Kick out" (quad) + knee jerk + medial leg
L5: "Big toe up" (EHL) + NO reflex + dorsum foot
S1: "Stand on toes" (calf) + ankle jerk + sole/lateral foot

Memory Aid:

L4 = 4-headed muscle (quads) + knee jerk
L5 = 5 toes (great toe up)
S1 = Stand (on toes), S for Soleus

Motor Testing

Key Motor Tests

L4 - Quadriceps (Knee Extension):

Patient seated, extends knee against resistance
Also test hip adductors

L5 - Extensor Hallucis Longus (Great Toe Extension):

"Bend your big toe up toward your head"
Most sensitive for L5 (isolated muscle)
Also test ankle dorsiflexion (tibialis anterior shares L4/L5)

S1 - Gastrocnemius/Soleus (Plantarflexion):

Single heel raise test (can they stand on toes?)
Plantar flexion against resistance
Also test hip extension (gluteus maximus)

Cauda Equina Examination

Mandatory Assessment

Always test in suspected disc herniation:

Saddle Sensation:

Test perianal sensation (S2-5)
"Is this numb compared to your thigh?"
Compare both sides

Anal Tone:

Digital rectal examination
Note resting tone and voluntary squeeze
Document in all cases of bilateral symptoms

Bladder Function:

Ask about retention (can't void), incontinence
Check for palpable bladder (distended)
Post-void residual if available

Differential Diagnosis

Disc Herniation

pain: Leg > back, dermatomal
slr: Positive 35-70°
motor: Myotomal weakness
reflex: Decreased at level

Lumbar Stenosis

pain: Both legs, neurogenic claudication
slr: Usually negative
motor: May be normal
reflex: May be decreased

Piriformis Syndrome

pain: Buttock to leg
slr: May be positive
motor: Normal
reflex: Normal

Hip OA

pain: Groin, anterior thigh
slr: Negative
motor: Normal
reflex: Normal

Spondylolisthesis

pain: Back > leg
slr: Variable
motor: May be affected
reflex: Variable

Tumor/Infection

pain: Constant, night pain
slr: Variable
motor: May be progressive
reflex: Variable

condition	pain	slr	motor	reflex
Disc Herniation	Leg > back, dermatomal	Positive 35-70°	Myotomal weakness	Decreased at level
Lumbar Stenosis	Both legs, neurogenic claudication	Usually negative	May be normal	May be decreased
Piriformis Syndrome	Buttock to leg	May be positive	Normal	Normal
Hip OA	Groin, anterior thigh	Negative	Normal	Normal
Spondylolisthesis	Back > leg	Variable	May be affected	Variable
Tumor/Infection	Constant, night pain	Variable	May be progressive	Variable

Summary Presentation

Viva scenarioStandard

Presenting Your Findings

Clinical prompt

“38-year-old man with 3-week history of left leg pain radiating to the lateral leg and dorsum of foot, worse with sitting.”

Examination Sequence

Systematic Approach

Observation: Posture, antalgic lean, muscle wasting
Gait: Antalgic, foot drop (L5), heel walk (L5), toe walk (S1)
Active ROM: Flexion, extension, lateral flexion
SLR: Both sides, note angle and distribution
Crossed SLR: If SLR positive
Bowstring: If SLR positive and want confirmation
Femoral stretch: If upper lumbar symptoms
Motor: Quads (L4), EHL (L5), calf (S1)
Sensory: Dermatomal distribution
Reflexes: Knee (L4), ankle (S1)
Cauda equina screen: Saddle, bladder, bowel

L4 vs L5 vs S1 Quick Reference

Pain Distribution

l4: Anterior thigh, medial leg
l5: Lateral leg, dorsum foot
s1: Posterior leg, lateral foot

Key Motor

l4: Knee extension
l5: Great toe extension
s1: Plantarflexion

Functional Test

l4: Squat and rise
l5: Heel walk
s1: Toe walk/single heel raise

Reflex

l4: Knee jerk decreased
l5: None reliable
s1: Ankle jerk decreased

Disc Level

l4: L3-4
l5: L4-5
s1: L5-S1

feature	l4	l5	s1
Pain Distribution	Anterior thigh, medial leg	Lateral leg, dorsum foot	Posterior leg, lateral foot
Key Motor	Knee extension	Great toe extension	Plantarflexion
Functional Test	Squat and rise	Heel walk	Toe walk/single heel raise
Reflex	Knee jerk decreased	None reliable	Ankle jerk decreased
Disc Level	L3-4	L4-5	L5-S1

Examiner Tips

Exam day cheat sheet

Scoring High in Lumbar Disc Examination

Do

Perform SLR correctly (straight leg, note angle)
Test EHL specifically for L5
Always screen for cauda equina
Use crossed SLR (highly specific)
Correlate motor, sensory, reflex to single root

Don't

Accept back pain as positive SLR
Miss cauda equina symptoms (medicolegal risk)
Confuse L4/L5/S1 patterns
Forget femoral stretch for upper lumbar
Neglect to ask about bladder/bowel