For humans, the evolutionary significance of walking upright is obvious: it freed our hands and promoted human intelligence. At the same time, walking upright has also had a profound effect on human body structure. For example, the position of the foramen magnum in the human occipital bone is more anterior than that of apes, which is probably the result of the change in the line of gravity as the human skeleton adapts to standing upright. Uprightness has also brought corresponding changes to the joints of the lower limbs. The knee joint is close to the ground and is almost the most weight-bearing joint except for the ankle. However, unlike the ankle, which is primarily weight-bearing, the knee is also involved in many important movements. Running, jumping, kicking, climbing, riding, etc. all rely on the knee joint to accomplish. Therefore, the knee joint not only needs to have a strong structure to maintain the weight, but also must have a dexterous design to meet the needs of activities. For athletes engaged in competitive sports, the state of the knee joint is often directly affect the professional life and competitive career. The bony structures that make up the knee are the distal femur, the proximal tibia, and the patella. However, these bony tissues do not contribute much to maintaining knee stability. It is the ligaments, menisci, muscles, and tendons located inside and outside of the joint that are the main forces that bind these bony tissues together. It is easy to explain why many athletes make a good recovery from a fracture, while those with ligament and meniscus injuries often have to regrettably bid an early farewell to the field. Muscle strains and contusions are also common, but because muscles have a better blood supply than ligaments, tendons and other tissues, and recover better with time and rest, muscle injuries generally do not interfere with athletic careers. In the knee joint, two ligaments are responsible for connecting the femur and tibia joint surfaces to each other. These ligaments are also known as cruciate ligaments or ACLs because they cross each other in a cross shape. When the knee is flexed, the anterior cruciate ligament prevents the tibia from moving forward and the posterior cruciate ligament prevents the tibia from moving backward, which ensures anterior and posterior stabilization of the knee joint during flexion. On the lateral side of the knee, there are the medial collateral ligament and the lateral collateral ligament, which are tightened when the knee is straightened, preventing the knee from stretching and rotating so that it doesn’t wobble when we stand. Between the articular surfaces, each knee also has 2 crescent-shaped fibrous cartilages called menisci. The menisci fill within the joint space, increasing the flexibility and stability of the joint and assisting in extension and rotation. Normally, the knee has a slight valgus of about 7 degrees, and when upright, the medial knee bears 60% of the load. As a result, the meniscus, collateral ligaments and anterior cruciate ligament are more closely related on the medial side of the knee, often resulting in a “triad” of injuries. However, weight is not the greatest force on the joint. In the completion of climbing, jumping and other movements, the patella and femur between the force can be as high as 5-8 times the body weight. The patella, commonly known as the knee, is a delicate design given to us by nature. It not only protects the knee joint, but also acts as a lever when pulling on the thigh muscles. Without the patella, we would have to exert 30% more force to accomplish a kick. Severe injuries to the patella often result in the patella having to be removed, which also greatly affects sports and quality of life. In addition to sports injuries, the knee joint wears out as we age and a variety of problems occur. It is therefore important to take good care of the knee joint from now on. Adequate preparation before exercise to avoid sudden large exercise; concentration during exercise to avoid trauma; choosing a flat and flexible sports ground, reducing weight, avoiding excessive impact on the knee joint when running; wearing the necessary protective equipment are all reasonable and effective measures. If the knee joint has been injured, it should be sufficient rest, try to avoid participating in those knee loaded sports activities such as mountaineering, climbing stairs and so on. Scientific exercise will help us to maximize the service life of the knee joint, so that we can pick up a cane later in our old age.