The knee is made up of three bones. First there is the femur, which is the largest bone in your body. Secondly, is a bone called the tibia, which connects to the femur by ligaments and a capsule. Lastly, a bone called the patella, or kneecap. It moves with the knee joint as the knee bends. Between the tibia and the femur is a C-shaped cartilage called the meniscus. Not only does it allow the two bones to slide over each other smoothly but it protects the joint. Outside the knee joint there is a bursa, which is a sac filled with fluid located between a bone, skin, tendon, or muscle. There are two cruciate ligaments located in the center of the knee joint. The anterior cruciate ligament and the posterior cruciate ligament. They are the major stabilizing ligaments of the knee. They prevent the femur and tibia from sliding out of place. In a way, they keep everything in place.