What a beautiful joint it is - the knee.
Three of the strongest bones - the femur, the tibia and the patella - converging at the most used structure of the body. Just two ligaments hold the femur to the tibia - the anterior cruciate ligament keeps the tibia from sliding forward during knee motion and at the same time the posterior cruciate ligament keeps the femur from sliding forward.
Two types of cartilage make motion even easier; the first, articular cartilage covers the ends of the bones and provides a smooth gliding surface.