import { HighYieldBox, ExamCheatSheet, Tabs, Tab, ComparisonTable, VivaScenario, ContentSection, SpecialTestCard , MedicalImage} from '@/components/content' # Knee Collateral Ligament Examination The collateral ligament examination requires systematic varus and valgus stress testing at both 0° and 30° flexion. Examiners expect you to understand why 30° testing isolates the collaterals, recognize the posterolateral corner (PLC), and identify combined injuries. ## Quick Reference One-Pager ## Anatomy **Medial Collateral Ligament (MCL):** - Origin: Medial femoral epicondyle - Insertion: Medial tibial metaphysis (4-5cm below joint line) - Superficial MCL: Primary valgus restraint - Deep MCL: Attached to medial meniscus - Resists valgus stress and external rotation **Lateral Collateral Ligament (LCL):** - Origin: Lateral femoral epicondyle - Insertion: Fibular head - Cord-like structure (distinct from lateral capsule) - Resists varus stress **Posterolateral Corner (PLC):** - LCL + Popliteus tendon + Popliteofibular ligament - Resists varus, external rotation, and posterior translation - Often injured with PCL ## MCL Examination **Why Test at 0° AND 30°:** - At 0° (full extension): Knee is "locked" - cruciates, capsule, and collaterals all contribute to stability - At 30° flexion: Knee is "unlocked" - cruciates are relaxed, collateral is the primary restraint **Interpretation:** - Laxity at 30° only = Isolated MCL injury - Laxity at BOTH 0° and 30° = Combined injury (MCL + cruciate/capsule) **Systematic Palpation:** 1. **Femoral origin**: Medial epicondyle (most common site of injury) 2. **Mid-substance**: Along medial joint line 3. **Tibial insertion**: 4-5cm below joint line on medial tibia **Associated Findings:** - Swelling over medial aspect - Ecchymosis (bruising) in acute injuries - Point tenderness at site of tear ## LCL Examination ## Posterolateral Corner (PLC) Examination ## Grading System ## Combined Injury Patterns **MCL + ACL ("Unhappy Triad" or O'Donoghue Triad):** - Classic: MCL + ACL + medial meniscus - Modern data: MCL + ACL + LATERAL meniscus more common - Valgus contact mechanism (e.g., football tackle) **LCL/PLC + PCL:** - Most common combined lateral injury - High energy (dashboard injury, hyperextension) - Dial test positive at 30° AND 90° - Always assess vascular status (popliteal artery) **Knee Dislocation (Multiligament):** - By definition: ACL + PCL injured (minimum) - Often includes collaterals - MUST assess vascular status - CT angiography - Reduction if still dislocated **Vascular Injury Alert:** Posterolateral corner injuries and knee dislocations have high risk of popliteal artery injury: - Always check distal pulses - ABI (Ankle-Brachial Index) if any concern - CT angiography for multiligament injuries - Even if pulses present, intimal injury possible ## Summary Presentation ## MCL vs LCL Injury Comparison ## Examiner Tips