Which ligament of the knee is the primary restraint against anterior displacement of the tibia on the femur, commonly torn in a valgus and external rotation injury?
- A Posterior cruciate ligament
- B Medial collateral ligament
- C Anterior cruciate ligament ✓
- D Lateral collateral ligament
Correct answer: C. Anterior cruciate ligament
Explanation
The anterior cruciate ligament (ACL) is the primary restraint to anterior tibial translation and is particularly vulnerable in deceleration-pivot injuries with valgus stress and internal rotation. A positive anterior drawer test and Lachman test confirm ACL disruption. The unhappy triad of O'Donoghue involves ACL, medial collateral ligament, and medial meniscus injury from a valgus-external rotation force.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.