Osteoarthritis (OA) is a chronic arthritic disease characterized by degeneration and loss of articular cartilage and regeneration of bone at the joint edges and subchondral bone, and is the most common cause of inflammation of the knee joint. Osteoarthritis of the knee is most common in the elderly population. Osteoarthritis of the knee is a disease in which degenerative changes in joint cartilage cause cartilage loss and destruction, accompanied by periarticular osteophyte reaction, also known as osteoarthrosis, degenerative arthritis, proliferative arthritis, hypertrophic arthritis, and age-related arthritis. 50% of people over 60 years of age have the disease, and 80% of people over 75 years of age have the disease, with more women than men, and the number is increasing. It is the second most common disease after coronary heart disease, and its cause is still unclear, but its occurrence may be related to age, obesity, inflammation, trauma and genetic factors. Primary osteoarthritis refers to joint lesions that are not associated with other diseases as we age, while secondary osteoarthritis is caused by injury, inflammation, genetics and metabolic endocrine diseases. The etiology of osteoarthritis is not entirely clear. However, it is generally believed to be related to aging, strain and trauma, inflammation, obesity, genetics, metabolism and immunity.1 Aging and aging2 Exercise, trauma and disuse3 Obesity4 Genetics5 Intraosseous hypertension6 T-2 toxin II. In the early stages, chondrocyte reduction, fatty degeneration and collagen fibrillation are seen on light microscopy, followed by most softening foci on the cartilage surface, loss of luster, yellowing of the cartilage, roughness and unevenness of the surface, and then fissures and surface exfoliation, resulting in exposure of the subchondral bone, and small fragments that can cause synovial inflammation. At the same time, the subchondral bone undergoes ivory-like changes and thickening in the largest part of the pressure and wear, and a bone redundancy is formed at the attachment of the cartilage marginal ligament, which is generally called bone spur, while the peripheral part of the bone under less pressure atrophies, and the X-ray shows osteoporosis, and sometimes cystic changes of different sizes can be seen in the subchondral bone, which are mucous-like and fibrinous due to microfracture of bone trabeculae. These are mucinous and fibrinous changes caused by microfractures of bone trabeculae. The most common symptom reported by patients with proliferative osteoarthritis of the knee is pain and stiffness in the knee joint, which is obviously characterized by pain and stiffness that is relieved by activity, but more severe when the pain starts to move. Other patients often complain of significant knee pain at night, which is often due to complications of intra-articular inflammatory lesions, resulting in joint capsule contracture and intraosseous congestion, leading to increased pressure in the medullary cavity. Some patients may have associated knee swelling and limited range of motion, and patients often complain of inability to straighten the knee joint and difficulty squatting. Thigh muscle atrophy or joint deformation may also be seen. Treatment methods 1. Non-surgical treatment Non-pharmacological treatment: for different patients, functional exercises, physical therapy (heat therapy, cold therapy, ultrasound, etc.) can be used to increase local blood circulation and relax muscles. Since the affected joints have the tendency to adapt, functional exercises are crucial. Some reports have shown that the combined application of multiple rehabilitation therapies can significantly improve the treatment effect of osteoarthritis of the knee. Drug therapy: For patients with osteoarthritis, control of joint pain is essential, but since no theoretical basis can still be found, the treatment of osteoarthritis of the knee is mostly used: (1) analgesics: paracetamol is the drug of choice for pain relief in OA. For patients with poor paracetamol efficacy or acute inflammatory exudate, non-steroidal anti-inflammatory drugs (NSAIDs) can be chosen. (2) Intra-articular medication: commonly used are glucocorticoids and hyaluronic acid (HA). (3) Chinese herbal medicine: pharmacodynamic studies of Chinese herbal medicine for osteoarthritis of the knee are actively underway, and different understanding of the etiology and pathology of osteoarthritis of the knee are used for internal and external application of Chinese herbal medicine, respectively. Prescription medication is based on medicines such as cow’s knee, angelica, rehmannia, astragalus, wei ling xian, licorice, white peony, dou huo, dulcimer, and chicken blood vine. 2. Surgical treatment: (1) Osteotomy: Osteotomy of the femoral condyle or tibia at a high level to change the biological force line of the knee joint, increase the joint space, change the joint load, achieve a reduction in intraosseous pressure, and promote the formation of a new joint surface, thus reducing joint pain. (2) Arthrocentesis: Arthrocentesis or arthroscopy is often performed clinically to remove the synovial membrane and free bodies from the joint, grind the bone, cartilage and degenerated meniscus, and then repeatedly flush the joint cavity to improve the intra-articular environment. (3) Arthroplasty: Arthroplasty is used for advanced osteoarthritis of the knee, severe deformity of the joint, degeneration of the articular cartilage, limitation of joint movement, and poor results of non-surgical treatment. Arthroplasty is divided into hemiarthroplasty, unicondylar replacement, and total knee replacement. Hemiarthroplasty is mainly used for young, obese, active patients and certain tibial plateau fractures, while total knee replacement or unicondylar replacement is not recommended. It requires a stable preoperative knee structure, a normal femoral condyle surface, and no significant deformities or soft tissue lesions. Unicondylar replacement is used only for patients whose lesions involve only one interval or unicondyle and whose knee ligaments are basically normal before surgery. Artificial total knee arthroplasty is mainly used in older, less active patients. In China, it has been reported that since the early 1970s, condylar-type artificial knee joints have been used clinically, and the success rate has been close to 90% after 10 years of follow-up. (4) Other therapies In recent years, cartilage, cartilage membrane or periosteal transplantation are being further applied in research.