Osteoarthritis is a relatively common chronic degenerative joint disease that can lead to joint pain and loss of function, so the treatment of osteoarthritis has been one of the important topics of research in the orthopedic field. In recent years, osteoarthritis has been treated with intracavitary injection of sodium hyaluronate (SH) into the knee joint and microwave treatment of the knee joint to improve joint function and relieve pain, with more satisfactory results. Treatment method: The patient is seated, the skin of the injection site of the affected knee is routinely disinfected, and the knee is punctured after local anesthesia, and the joint fluid is withdrawn after entering the joint cavity. After the injection is completed, the knee joint should be moved passively so that SH is evenly distributed on the surface of the affected knee joint. Microwave therapy is used once a day for 10-14 days for knee joint treatment. SH is a polymeric polysaccharide formed by the polymerization of disaccharide units composed of glucuronic acid and acetylamino acid, which is one of the main components of synovial fluid and cartilage matrix. SH in the joint cavity has many important functions such as maintaining the viscosity of the joint fluid, lubricating the bone and joint by keeping it on the surface of the articular cartilage, and nourishing the cartilage. When suffering from osteoarthritis, SH will be hydrolyzed by hydrolytic enzymes, resulting in a decrease in the concentration of SH, thus making the joint lesion more and more serious. If exogenous SH preparations with high molecular weight, high concentration and high viscoelasticity can be supplemented in time, it will play a positive role in the recovery of joint function. Based on this principle, its use in the treatment of osteoarthritis has significant efficacy. SH has several main effects: it increases the SH content in the joint cavity, re-establishes the natural barrier, prevents further destruction of the cartilage matrix from disappearing, and inhibits the precipitation of proteoglycans from the cartilage matrix. It also inhibits leukocyte mobile chemotaxis, reduces synovial permeability, and decreases intra-articular exudate. The unique gel property of SH can produce a greater affinity between joint fluid and articular cartilage, which can closely adhere to the joint surface and play a lubricating role, thus reducing resistance to joint movement and protecting articular cartilage from excessive mechanical wear. SH can promote the repair of superficial articular cartilage, maintain the thickness of uncalcified cartilage, and protect the damaged cartilage from degenerative changes that have just occurred. Microwave is a centimeter wave, the position in the electromagnetic spectrum between ultra-short wave and light wave, microwave therapy to radiation field method of action on the human body, the tissue ion dipole with the frequency of microwave oscillation at high speed, resulting in displacement current, this high-frequency electromagnetic field energy, can penetrate the knee joint and be absorbed by the thermal effect, there is improved blood circulation to the knee joint, inflammatory mediators such as histamine, bradykinin, etc. has inhibited its It has a positive effect on improving blood circulation in the knee joint, inhibiting the synthesis of inflammatory mediators such as histamine and bradykinin, etc., and facilitating the absorption of inflammation while reducing synovial leakage.