What is the purpose of the posterior cruciate ligament (PCL)?

The purpose of the posterior cruciate ligament (PCL) is to resist forces that push the tibia (shin bone) posteriorly relative to the femur (thigh bone). This ligament plays a key role in maintaining knee stability, particularly during activities that involve pivoting or sudden changes in direction. The PCL works in conjunction with the anterior cruciate ligament (ACL) to control knee movements and support the joint under stress. By limiting excessive backward translation of the tibia, the PCL helps to prevent injuries that could occur during sports or physical activities, especially those involving sudden stops or sharp turns.

The other options do not relate to the PCL's primary function. The acromio-clavicular joint stability is managed by different ligaments, and stability during ankle rotations is not the responsibility of the PCL, which is specifically associated with the knee joint. Thus, identifying the correct role of the PCL clarifies its significance in maintaining knee integrity and function.