The knee is a joint that consists of three bones. The thigh bone (Femur), the leg bone(tibia) and the knee cap (patella). The joint means a confluence (meeting point) of two bone. The thigh and leg bone glide over each other facilitating bending and straightening of the knee. The knee cap glides over the thigh bone and has the all important muscles attached to it , acting as a lever to facilitate movement of the joint.