What is the primary function of the PCL?

The primary function of the posterior cruciate ligament (PCL) is to stabilize the knee during flexion. This ligament is situated in the center of the knee joint, crossing behind the anterior cruciate ligament (ACL). Its role is particularly crucial when the knee is bent, as it helps maintain the alignment of the femur and tibia under load.

When the knee is flexed, the PCL prevents the femur from sliding forward on the tibia, which is essential for stabilizing the joint during activities that involve bending, such as running or squatting. This stabilizing function is vital in preventing injuries and ensuring proper movement mechanics, making the PCL an essential component of knee stability during flexion.

In contrast, while the other options describe various aspects of knee function, they do not accurately capture the primary role of the PCL in flexion. The ligament does help control some aspects of rotation and may provide support in conjunction with the ACL, but its main job is centered on stability during flexed positions of the knee.