In a knee injury where the patient describes a 'pop' followed by pivot shift phenomenon (anterior subluxation of the lateral tibial plateau on the femur with extension and internal rotation), which primary restraint has been disrupted?

• A Anterior cruciate ligament (ACL) ✓
• B Posterior cruciate ligament (PCL)
• C Medial collateral ligament (MCL)
• D Iliotibial band

Explanation

The anterior cruciate ligament is the primary restraint to anterior tibial translation and internal tibial rotation on the femur. The pivot shift test exploits this — the lateral tibial plateau subluxes anteriorly under applied valgus and internal rotation, then reduces with a clunk as the knee moves into flexion. PCL disruption produces a posterior sag (posterior drawer). MCL injury causes valgus instability. The iliotibial band contributes to the pivot shift but is not the primary stabilizer.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.