When we stand upright with our feet together, the pelvis is wider than the sum of the width of the two feet, and the two feet have to be tucked inward to stay together. Therefore, the gravity of the upper body is not transmitted down through the medial femur. This is especially true during walking, supported upright on one foot. When the lower limb is upright, the knee joint is kept straight by the pull of the anterior and posterior muscles. The gravity of the upper body is transmitted vertically down through the femoral head along the femoral stem to the femoral epicondyle. When walking, there is a process of flexion and then extension of the knee joint. The forward-moving leg acts on the iliopsoas muscle, the lower limb flexes the hip, the lower end of the femur lifts forward, the knee joint relaxes and bends, and the lower leg drops and swings gently back. The body weight is shifted forward by the action of the supporting leg. The foot leaves the ground and hangs in the air. At the end of the backward swing of the lower leg, the foot touches the ground with the quadriceps pulling forward. When the forward leg touches the ground and straightens, the body is first tilted outward, the femoral epicondyle is supported by the weight, the distance between the femoral and tibial medial condyles widens, the distance between the inner condyle edge of the joint is maximized, and the inner wall of the joint capsule is pulled. Then the body is tilted inward, and the spaced-out medial femoral condyle smashes down on the medial tibial condyle. Both femoral condyles simultaneously bear weight to support the body and the knee is straightened. This process is done almost instantaneously. This lateral joint sway is a physiological necessity for walking, not a so-called knee instability. This occurs in young people, although there is repeated smashing of the medial femoral condyle against the medial tibial condyle. In young people there is no significant damage due to the cushioning of the very thick cartilage of the joint surface and meniscal cartilage. Clinically, it presents as pain and swelling in the medial knee. Despite the pain, there will be no bone changes on the x-ray. This is not the case in middle-aged and elderly people. Due to middle-aged and elderly people, their physique ages and the brittleness of the peri-knee tissue increases. During repeated alternation of the legs while walking, the medial knee wall (joint capsule, lateral ligaments, fascia, etc.) is repeatedly stretched beyond the limit, and then a slight tear injury and edema around the injury occurs. After years of smashing, the articular surface cartilage and meniscal cartilage are damaged out. Basically, a smash between the medial femoral condyle and the medial tibial condyle bone is formed. In the early stages, there is edema and necrosis of the bone, and over the years, there is an accumulation of bone scarring (so-called osteophytes). On X-rays it appears as narrowing of the joint space and osteophytes on the inner edge of the joint. Since there are no nerves in the bone, it does not cause pain. Edema of the soft tissues around the bone caused by osteoedema and edema of the joint capsule wall from strain injury are the causes of medial knee pain. Articular cartilage damage, necrosis and liquefaction as well as synovial edema and oozing are the causes of joint effusion. Why does bone redundancy not cause pain? One, there are no nerves in the bone tissue and no pain is felt. Secondly, after a bone growth, it will always be there and will not disappear. Knee joint pain is not always painful. Generally, there is no pain when the knee joint is not moving, and it is the soft tissues, not the bone, that change in shape. From the above description, we can know that there are two causes of knee pain, one is injury to the wall of the joint capsule. This includes the joint capsule, ligaments and fascia. The second is the painful distention of the joint capsule wall due to the compression of the joint fluid. Both causes can be present at the same time, or they can be present separately. In other words, changes in the shape of the joint capsule wall are the cause of knee pain. Once the cause is known, treatment is simple. No medication is needed, just keep the knee joint in a pain-free state for a period of time and it will heal on its own. All medications that are currently claimed to treat the knee are painkillers. The characteristic is that they do not hurt when you take them, but hurt when you stop taking them. Therefore, it is better not to take them as much as possible. Only if the pain affects your sleep, you can take painkillers once a day before going to bed. All painkillers, creams, massages, bruises, liquor application, sprays, physical therapy (heat therapy), closure, cupping, acupuncture, small needles, etc. All can aggravate the pain and prolong the pain in different ways.