When we have swollen joints and go to the doctor, the most common thing we hear is synovitis. What is synovium and what is synovitis a disease? First of all, our joint is a cavity, and every time we do a movement in our knee joint, there will be a sliding of the joint surface, and what is the joint surface? This is the most important structure of our joints, joint cartilage is non-renewable, just like our teeth, fall off is not re-grown, if the joint surface is not smooth, it is the bone grinding bone, you can imagine, we are so big weight, pressed on such a small joint surface, how much pain, this is the cause of most elderly joint pain. Since our joint cartilage is so important, our body will not easily let it go wrong. Otherwise, we humans would not be eliminated. Therefore, our joints will have other structures to protect our joint cartilage, the three most important ones are: synovial membrane, meniscus, and joint ligaments. What is the role of the synovial membrane? It secretes lubricant to our joints. You can imagine what would happen if the axle had no lubricant. The normal synovial membrane is on the wall of our joint capsule, invisible to the naked eye, and works diligently every day to secrete joint fluid to nourish and moisturize our joints. However, just like our weather changes, there are sunny days and occasionally cloudy days and rain. The small environment of our knee cavity also changes, for example, when bacteria come in, and our synovial membrane is the soldier that protects this environment to defend the stability of our joint cavity environment. It secretes a lot of synovial fluid, which contains defense factors for our immune system to defend against external bacteria. When too much synovial fluid is secreted, our joints look swollen. This is the pathogenesis of synovitis and why our joints swell up. After a battle, it’s a mess. The environment within our joints has changed and the articular cartilage is in an abnormal state of nutrition. The synovial membrane of the joint is enlarged, so how do you get it to go back down. First of all, the conservative treatment is to brake the knee joint in the straight position and use some medicine to reduce the swelling, in short, rest and braking is the fundamental principle. If the swelling does not go down after a month or two months, we need to do something about the synovial membrane, arthroscopic surgery to remove the synovial membrane, and then carefully clean the knee cavity.