Posterior cruciate ligament (PCL) injury happens far less often than does injury to the knee’s more vulnerable counterpart, the anterior cruciate ligament (ACL). The posterior cruciate ligament and ACL connect your thighbone (femur) to your shinbone (tibia). If either ligament is torn, it might cause pain, swelling and a feeling of instability.

https://www.mayoclinic.org/diseases-conditions/pcl-injury/symptoms-causes/syc-20354855