Knee Cruciate Ligament Examination
The cruciate ligament examination is a fundamental orthopaedic skill. Examiners expect you to perform the Lachman test correctly (gold standard for ACL), recognize the importance of endpoint quality, and understand the posterior sag sign for PCL injuries. The pivot shift test demonstrates rotatory instability and correlates with functional symptoms.
Quick Reference One-Pager
ACL Tests
- Lachman test (gold standard, 85% sens)
- Anterior drawer (less sensitive due to hamstring guarding)
- Pivot shift (functional instability, best under anesthesia)
PCL Tests
- Posterior drawer test
- Posterior sag sign (Godfrey)
- Quadriceps active test
- Dial test (combined PLC injury)
Key Concepts
- Endpoint quality is critical (firm vs soft)
- Compare with opposite side
- Effusion reduces test sensitivity
- Combined injuries more common than isolated
Grading
- Grade I: 0-5mm (partial)
- Grade II: 5-10mm (complete)
- Grade III: greater than 10mm (combined injury)
ACL Examination
Primary Tests
Special test
Lachman Test
ACL integrity (GOLD STANDARD)
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Technique
- 1Patient supine, knee flexed 20-30°
- 2Stabilize distal femur with one hand (thumb on lateral, fingers medial)
- 3Grasp proximal tibia with other hand (thumb on tibial tubercle)
- 4Apply anterior translation force to tibia
- 5Assess amount of translation AND endpoint quality
Positive Sign
Increased anterior translation with soft/mushy endpoint (compare to opposite side)
Indicates
ACL rupture
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Endpoint Quality:
- Firm endpoint = ACL intact (even with some laxity may be constitutional)
- Soft/mushy endpoint = ACL ruptured
The endpoint is MORE IMPORTANT than the amount of translation for diagnosing ACL rupture.
Special test
Anterior Drawer Test
ACL integrity
Technique
- 1Patient supine, hip flexed 45°, knee flexed 90°
- 2Foot flat on bed, stabilized by examiner sitting on it
- 3Hands around proximal tibia, thumbs on joint line
- 4Pull tibia anteriorly
Positive Sign
Increased anterior translation (greater than 6mm or compared to opposite side)
Indicates
ACL rupture (less sensitive than Lachman - hamstrings guard, ACL fibers not optimally tensioned)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Why Lachman is Better Than Anterior Drawer
- Less hamstring guarding at 20-30° flexion
- ACL is more vertically oriented at 20-30° (more anterior force on ligament)
- Easier to perform with acute effusion
- Less pain than testing at 90° flexion
Special test
Pivot Shift Test
Anterolateral rotatory instability (functional ACL test)
Technique
- 1Patient supine, leg fully extended and relaxed
- 2Hold foot in internal rotation
- 3Apply valgus stress to knee
- 4Slowly flex the knee from full extension
Positive Sign
Clunk or jerk at 20-40° flexion as tibia reduces from subluxated position
Indicates
ACL deficiency with anterolateral rotatory instability. The tibia subluxates anteriorly in extension and reduces at 20-40° as IT band moves posterior to axis of rotation
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Pivot Shift Grading
- Finding
- Negative
- Finding
- Glide (subtle shift)
- Finding
- Clunk (clear reduction)
- Finding
- Gross shift with locking
Clinical Correlation:
- Pivot shift correlates with functional instability (giving way during activities)
- May be negative in awake patient due to guarding
- Often becomes positive under anesthesia
Additional ACL Tests
Special test
Lever Sign (Lelli Test)
ACL integrity (alternative test)
Technique
- 1Patient supine, knee extended, leg relaxed
- 2Place clenched fist under proximal calf (acts as fulcrum)
- 3Push down on distal femur
Positive Sign
Heel does not rise off bed (normally ACL pulls tibia posteriorly, raising heel)
Indicates
ACL rupture
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
PCL Examination
Primary Tests
Special test
Posterior Drawer Test
PCL integrity
Technique
- 1Patient supine, hip flexed 45°, knee flexed 90°
- 2Foot flat on bed
- 3First assess for posterior sag (step-off)
- 4Push tibia posteriorly
- 5Compare with opposite side
Positive Sign
Increased posterior translation. Critical: First check if tibia is already posteriorly subluxed (sag)
Indicates
PCL rupture
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Critical Point: Before performing posterior drawer, look for POSTERIOR SAG. If the tibia is already posteriorly subluxed, you may incorrectly interpret anterior translation during "anterior drawer" as positive - this is actually the tibia reducing to neutral!
Special test
Posterior Sag Sign (Godfrey Test)
PCL integrity (gravity-based)
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Technique
- 1Patient supine, both hips and knees flexed to 90°
- 2Examiner supports both heels together (or patient's feet rest on examiner's shoulder)
- 3Observe tibial plateau position from the side
Positive Sign
Affected tibia sags posteriorly compared to uninjured side (posterior step-off)
Indicates
PCL rupture
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Special test
Quadriceps Active Test
PCL integrity
Technique
- 1Patient supine, knee flexed 60-90°
- 2Observe starting position (posterior sag if PCL deficient)
- 3Ask patient to contract quadriceps (attempting to extend knee) while you resist
Positive Sign
Tibia moves anteriorly (reduces from posteriorly subluxed position)
Indicates
PCL rupture (quadriceps vector pulls tibia anteriorly)
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Combined Injuries
Special test
Dial Test (External Rotation Test)
Posterolateral corner injury (+/- PCL)
Technique
- 1Patient prone, both knees flexed to 30° then to 90°
- 2Externally rotate both feet simultaneously (comparing tibial external rotation)
- 3Measure rotation at 30° and 90°
Positive Sign
Greater than 10° increased external rotation on affected side
Indicates
Increased at 30° only = Isolated posterolateral corner. Increased at BOTH 30° and 90° = PLC + PCL
Diagnostic Accuracy
Ability to detect true positives
Ability to exclude false positives
Combined Injury Patterns
PCL + PLC (Posterolateral Corner):
- Most common combined injury with PCL
- Dial test positive at 30° AND 90°
- Increased varus at 30° (LCL component)
ACL + MCL:
- Common in valgus contact injury
- Test valgus stress at 30° (MCL)
- Valgus stress positive at 0° = combined ACL + MCL
Multiligament Injury (Knee Dislocation):
- ACL + PCL minimum
- Always assess vascular status (popliteal artery)
- CT angiography mandatory
Grading System
- translation
- 0-5mm
- significance
- Partial tear
- endpoint
- May be firm
- translation
- 5-10mm
- significance
- Complete isolated tear
- endpoint
- Soft (ACL)
- translation
- greater than 10mm
- significance
- Combined ligament injury
- endpoint
- Soft, gross instability
Summary Presentation
“23-year-old female netball player who felt a 'pop' while landing from a jump. Immediate swelling.”
Clinical Pearls
Examination Tips
Acute ACL Injury:
- Hemarthrosis develops within 2 hours
- 70% of acute hemarthroses have ACL injury
- Lachman is more reliable than anterior drawer in acute setting
Chronic ACL Injury:
- May develop secondary meniscal tears
- Quadriceps wasting
- Pivot shift more easily elicited (less guarding)
PCL Injury Tips:
- Often missed - always look for posterior sag
- Isolated PCL may not require surgery
- Combined injuries need surgical consideration
Examiner Tips
Do
- Demonstrate Lachman confidently with proper technique
- Assess endpoint quality and describe it
- Compare with contralateral side
- Check for posterior sag before posterior drawer
- Test for combined injuries (dial test, collaterals)
Don't
- Forget to describe endpoint quality
- Miss posterior sag and misinterpret anterior drawer
- Skip the pivot shift test
- Test only one cruciate without excluding the other
- Forget vascular assessment in multiligament injury