The knee is the largest joint in the human body, very shallowly positioned and structurally complex, like a cross-link, and can be associated with almost any activity that uses the legs. The knee joint consists of the tibia, femur, and patella, and the surfaces of each of these bones are covered with a smooth layer of cartilage that acts like a cushion to provide cushioning and protection, and it allows the adjacent bones to slide relative to each other. The most common type of knee injury is osteoarthritis, which is mainly characterized by joint pain, stiffness, swelling and deformity. The incidence rate is significantly higher in the north than in the south, and higher in women than in men, mainly due to changes in hormone levels in women after menopause, resulting in increased brittleness of joint cartilage. Protecting the knee joints to master the four elements Element 1: Do not take climbing and going up and down the stairs as a method of exercise. Warm up before exercising, and engage in more flexible exercises such as swimming. Element 2: Avoid weight-bearing exercises, such as lifting heavy food. Obese people should mainly lose weight. Element 3: Wear less high heels to reduce the impact on the knee joint. Element 4: Seek early medical attention. If you already have osteoarthritis of the knee, you can take some glucosamine orally at an early stage to try to slow down the progress of the disease, and you can go to the hospital to do physical therapy for more obvious pain.