There are many reasons for knee joint effusion, and the time for elimination of knee joint effusion caused by different reasons is different. If the knee joint effusion is caused by common knee synovitis, the amount of effusion is relatively small, it can subside naturally in about 6 weeks. If the amount is relatively large, it is difficult to subside naturally, and the joint fluid can be extracted through the method of joint puncture and aspiration, which can quickly relieve the patient’s knee joint swelling, pain and other clinical symptoms. If the joint fluid is difficult to subside due to knee joint union, and the joint fluid caused by rheumatoid arthritis, it is also more difficult to subside, and joint puncture should be carried out to extract the joint fluid. In addition to arthrocentesis, oral medication, such as medication to activate blood circulation and remove blood stasis, reduce swelling and pain, can also promote the absorption and subsidence of joint effusion, as well as physical therapies, such as TDP baking lamps, localized hot compresses and so on, can also eliminate joint effusion.