Posterior cruciate ligament (PCL) injuries occur when there is damage to the PCL, one of the four major ligaments in the knee joint. The PCL connects the thighbone (femur) to the shinbone (tibia) and helps to stabilize the knee joint during movement. PCL injuries are less common than injuries to other ligaments in the knee, such as the anterior cruciate ligament (ACL), but they can still occur and can be quite debilitating.