What could cause posterior cruciate ligament (pcl) injury?

Force! The PCL is probably the strongest ligament in the knee. It requires a significant amount of force or energy to cause it to tear. Pcl tears are far less common than anterior cruciate ligament (acl) tears.
Accidents and falls. Pcl injuries are typically caused by knee dislocations, car accidents when the knee hits a dashboard, and falls directly onto the bent knee. Anything that would case the leg (tibia) to move backwards from a directly blow could cause a PCL injury.