The area behind the knee is called the posterior cruciate ligament (PCL), and it connects the femur, or thigh bone, to the tibia, or shin bone. The ligament prevents the tibia from moving backward to a point that can cause injury, according to the American Academy of Orthopaedic Surgeons.
PCL injuries sometimes occur in athletes who land on a bent knee or who hyperextend the knee while jumping, according to the National Institutes of Health. PCL injuries also occur in car accidents where individuals suffer trauma to their bent knees while they are sitting in the car. Because PCL injuries usually are caused by severe trauma, the knee often suffers additional injuries.