Not only is the knee the largest joint in the human body, it is also the most complicated. The knee is a hinge joint that is formed to move only on one axis. It is reinforced with both internal and external ligaments to give it a wide range of motion. It is strong and durable enough to support the body's weight with only slight reinforcement from other bones. It acts as a shock absorber due to fibrocartilage that is between the femur and tibia. This fibrocartilage protects the bones when running or doing other flexion activities.
The knee joint is a classic example of a synovial joint. The junction of the femur and tibia bones are enclosed in a joint capsule, lined with synovial tissue, encasing synovial fluid and two shock absorbing cartilage pads. The joint capsule is protected by the patella, or kneecap. So, the complete knee joint is a complex mechanism composed of muscles, ligaments, tendons and bones.