Which ligament prevents posterior translation of the tibia relative to the femur?

• A. PCL
• B. ACL
• C. MCL
• D. LCL

Answer: (A)

The key idea is that knee posterior stability is mainly provided by the posterior cruciate ligament. The PCL runs from the back of the tibial plateau up to the medial part of the femoral condyle in a orientation that resists the tibia moving backward relative to the femur, especially when the knee is flexed or loaded. This makes it the primary restraint to posterior tibial translation. In contrast, the anterior cruciate ligament prevents the tibia from moving forward (anterior translation), while the medial and lateral collateral ligaments mainly resist valgus and varus forces and do not primarily control posterior tibial movement. Therefore, the ligament preventing posterior translation of the tibia relative to the femur is the posterior cruciate ligament.