The largest and most complex joint in the human body is the knee. The knee joint is also the most complex and largest joint in the human body and plays a very important role in the body for support, stabilization and movement. The knee joint consists of the upper end of the tibia, the patella and the lower end of the femur. The outside of the knee joint is surrounded by a thin, loose joint capsule, which serves as a stabilizing and stabilizing device, and the surrounding ligaments include the patellar ligament, the fibular collateral ligament, the tibial collateral ligament, the anterior cruciate ligament, and the posterior cruciate ligament. Inside the knee joint capsule, there is articular cartilage and meniscus attached to each bone of the joint, the articular cartilage has a very good shock absorption, cushioning pressure of the elastic cushion role, is the human body is more prone to injury and is not easy to restore the part. The knee joint capsule cavity is filled with synovial fluid, which plays a role in lubricating and reducing the friction of the articular cartilage when the knee joint is in motion. Warm tips: knee cartilage and meniscus lack of nerves, blood vessels structure, in the injury is not easy to recover, each exercise should be done before the full preparation warm-up exercise, to reduce the possibility of injury.