Which ligament checks backward displacement of the femur on the tibia?

• A. Posterior cruciate ligament
• B. Medial collateral ligament
• C. Anterior cruciate
• D. Lateral collateral ligament

Answer: (C)

The knee’s stability in forward-backward translation is governed by the cruciate ligaments. The anterior cruciate ligament resists anterior translation of the tibia relative to the femur, which means it stops the tibia from moving forward and, in turn, prevents the femur from sliding backward on the tibia. That makes it the appropriate restraint for the described backward displacement of the femur on the tibia. The posterior cruciate ligament mainly resists backward movement of the tibia, not the described motion, and the collateral ligaments are more about resisting valgus/varus forces rather than anterior-posterior translation.