The knee joint is one of the largest joints in the body, consisting of the femur, tibia and patella. It is the body’s weight-bearing joint and one of the most vulnerable joints. The knee joint is the joint with the highest prevalence in the body. Knee pain is not only related to various pathologies within the joint, but is also often caused by various extra-articular factors. The symptoms that arise in the knee are often non-specific. Symptoms such as pain, tender leg, and joint interlocking can be caused by either cruciate ligament or meniscal injury, or by patellofemoral abnormalities, articular cartilage lesions, or may even be caused by mere ingrowth of abnormal hyperplastic synovium. The main knee diseases include: osteoarthritis, synovitis, patellofemoral cartilage, meniscal injury, etc. The knee is the most important “weight-bearing joint” in the lower extremities of the human body. The main causes of knee injuries: age-related degeneration and excessive weight bearing on the knee joint. The average pressure on the cartilage in the knee is 1/2 to 1 times more when standing or walking on a level surface, 2 times more when walking up stairs, and 7 times more when walking down stairs. The dangers of knee disease: Osteoarthritis of the knee is the most common and most important joint disease. If left untreated, osteoarthritis of the knee can lead to joint deformity and disability. Typical X-ray manifestations of osteoarthrosis of the knee: Joint space narrowing, subchondral bone plate sclerosis and bone redundancy formation are the basic X-ray features of osteoarthritis. In the early stages of osteoarthritis, when there are only degenerative changes in the cartilage, the X-ray may not show any abnormalities. As the articular cartilage becomes thinner, the joint space becomes progressively narrower, and the narrowing of the space can be disproportionately altered. The tibial plateau and femoral condyles become osteophytes, the intercondylar ridge becomes sharp, and the joint space is narrowed. Clinical manifestations of osteoarthrosis of the knee Pain: almost all cases have knee pain, pain characteristics: activity pain, continuous pain, night pain, pain is mostly related to temperature, air pressure, environment, emotions, aggravated in autumn and winter, aggravated when the weather changes. The pain is mostly located between the patellofemoral area or around the condyles, and on the medial side of the knee. It is less common on the lateral or posterior side of the knee. Swelling: due to soft tissue degeneration and hyperplasia, joint effusion and synovial hypertrophy, fat pad enlargement, etc., or even due to osteophytes and bone growth. Swelling of the suprapatellar capsule and infrapatellar fat pad is more common, but can also be a swelling of the whole knee. Deformity: inversion of the knee joint due to narrowing of the medial knee gap. Functional impairment: difficulty going up and down stairs, difficulty standing up from squatting. The functional impairment caused by osteoarthritis can be divided into abnormal coordination of joint movement and changes in the range of motion of joint flexion and extension. The vast majority are functionally limited, and permanent and complete loss of joint function is rarely seen. How to prevent osteoarthritis of the knee! 1, reduce weight, reduce the weight-bearing burden on the knee joint; 2, pay attention to warmth, avoid swimming and cold; 3, avoid climbing mountains, stairs, playing tai chi, brisk walking, running, square dancing, playing ball and other strenuous sports; 4, active treatment of osteoporosis, endocrine abnormalities and other diseases. Active and beneficial exercise! 1, advocate walking, generally recommended for about 30 minutes, with a break in between to sit for 5 minutes; 2, swimming (summer only, avoid warm water swimming) 3, no weight-bearing position joint flexion and extension activities.