Posterior Cruciate Ligament (PCL) is one of the ligaments that joins the thigh bone to the shinbone. It is located at the back of the knee. Along with other ligaments of the knee, it maintains stability and prevents the thigh and shin bones from moving out of the place. It takes a powerful force to injure your PCL, and they are caused by a blow to your knee front when bent.
It could happen by extending the knee beyond its normal range of movement, direct contact with the opponent while playing sports and falling forward with the knee bent.