In the clinic, we encountered many patients who had repeated swelling of the knee joint and were diagnosed with “synovitis” and were given repeated pumping, but soon swelling appeared again, then pumping, then swelling again, thinking that the knee joint problem could be solved by pumping, but in reality “synovitis of the knee joint” is a very general concept. In reality, “knee synovitis” is a very general concept, which can be summarized as “synovitis” because of the exudation of the synovial membrane of the knee joint caused by various diseases, fluid accumulation, and joint swelling, so the main thing for this type of patients is to find out the cause of the fluid accumulation, and by treating the cause, “synovitis Therefore, the most important thing for this type of patients is to find out the cause of the effusion, and by treating the cause, the “synovitis” will disappear. The most common clinical condition is meniscal injury, ACL injury, etc. These patients have a history of sprains, often for more than 1 year. These synovitis, in fact, are traumatic synovitis, the root cause of which is the constant wear and tear of the knee joint caused by meniscal injury, cruciate ligament injury, etc., causing synovial hyperplasia of the knee joint, resulting in repeated and constant swelling and effusion of the knee joint. There is another condition, synovial crease syndrome, because the synovial crease in the patellofemoral joint is hyperplastic, causing pain in the knee joint when bending and squatting, and also causing synovial hyperplasia, fluid accumulation, and joint swelling, which also needs to be removed by arthroscopy, and the joint will no longer accumulate fluid repeatedly. Therefore, my suggestion is that patients with swollen knee joints should first give a comprehensive examination and diagnosis to a knee specialist in the early stage, and should not pump fluid without doing any examination, so as not to cause infection of the joint. If the diagnosis is confirmed as meniscus and other injuries, synovial crepitus syndrome, etc., arthroscopic surgery is needed as soon as possible!