The ACL is called the anterior cruciate ligament of the knee and the PCL is the posterior cruciate ligament, which is also called the cruciate ligament of the knee because it is in the shape of a cross inside the knee joint. The ACL prevents forward displacement of the tibia and rotation of the lower leg, while the PCL controls backward displacement of the lower leg and rotation of the lower leg, regardless of the angle of the knee, whether it is straight or flexed. If there is an ACL injury or rupture, the symptoms are different from those of posterior cruciate ligament injury, as ACL injury is usually accompanied by collateral ligament and meniscus injury.