Your knee is made up of bone, cartilage, and ligaments. Muscles and tendons help the knee joint move. The knee joint actually consists of two joints. The first is called the patello-femoral joint, and this is where the large bone of the upper leg, known as the femur, connects with the knee-cap, called the patella. The second joint is the tibio-femoral joint, where the femur hinges with the large bone of the lower leg, called the tibia.
The knee is cushioned by cartilage that covers the ends of the tibia and femur, as well as the underside of the patella. Pads of cartilage that further serve to cushion the knee joint, called the lateral meniscus and medial meniscus, act as shock absorbers between the bones.
Ligaments help to stabilize your knee. The medial and lateral collateral ligaments run along the sides of the knee and limit sideways motion.
The anterior cruciate ligament, or ACL, and the posterior cruciate ligament, or PCL, connect the tibia to the femur at the center of the knee. The ACL connects from the front of the tibia to the back of the femur. Its function is to limit rotation and forward motion of the tibia
The PCL connects from the back of the tibia to the front of the femur. The function of the PCL is to prevent backward movement of the tibia on the femur. It also provides rotational stability to the knee joint.
These components of your knee, along with the muscles of your leg, work together to manage the stress your knee receives as you walk, run and jump.