The knee joint is a hinge joint. It is formed by two bone ends: these are the bottom of the femur and the top of the tibia. At the front is the kneecap. The ends of this are covered with a layer of cartilage so that the knee moves smoothly. On the inside and outside of the knee is the meniscus: a kind of pad. In the middle of the knee joint are the anterior and posterior cruciate ligaments. These prevent the lower leg from sliding forward or backward during walking and twisting movements.