KNEE The knee is a complex joint made up of three bones in a hinge formation: the patella (kneecap), the end of the femur (thigh bone), and the top of the tibia (shin bone). These bones articulate with each other forming the three 'compartments' of the knee. In a healthy knee a highly specialised and naturally lubricated cartilage covers the surface of the bones in the joint and lets the joint surfaces glide smoothly over each other. This joint is controlled by groups of powerful muscles of the thigh and the leg.