Knee arthroscopy is most commonly used for meniscal injuries and knee cleanouts. Arthroscopic procedures generally require saline irrigation. Only by maintaining adequate perfusion pressure can the joint cavity be sufficiently dilated and opened so that a good view can be obtained. Also, the perfusion pressure can be used to control intraoperative bleeding and allow the surgical field to avoid the interference of blood leakage. Therefore, after knee arthroscopy, there will be some edema and fluid accumulation in the knee cavity. There will also be some bleeding after arthroscopy. As a result, many patients often feel swelling and fluid accumulation in the knee joint after surgery. We call this process the “post-arthroscopic inflammatory response”. This inflammatory response period is not related to infection, but has three pathological phases: reactive synovitis, aseptic inflammation, and functional recovery. In general, this process takes 3-6 months. The main cause is the disruption of sympathetic response due to pressure shift in the joint cavity. Its clinical manifestations are: unrelieved or worsened knee pain, fluid accumulation in the knee joint, and limited extension and flexion activities. It is interesting to note that this reaction period is not related to the severity of the surgical trauma, but to the age and gender of the patient. The reaction is much more severe in women than in men and becomes more pronounced the older they are. The need for systematic functional exercises after surgery will significantly improve the swelling of the knee, especially the knee swelling. Many patients are often very concerned about knee effusion after surgery and hope to resolve the effusion by puncture, but if they do not perform muscle training carefully, they will find a recurrence of knee effusion back soon after puncture. This is because good functional exercise can improve the local circulation of the knee joint and bring the secretion and absorption of joint fluid in the knee cavity into balance, so that the knee joint effusion will absorb itself. Many patients, after the knee pain has been significantly relieved, tend to neglect functional training of the knee joint, which is a common problem and needs to be emphasized. Muscle training often needs to be performed for six months and should only be stopped after the muscles of both thighs have recovered to be essentially the same. For most patients, knee puncture therapy is required at 1.5, 3, 6, and 12 months postoperatively. For all patients, a follow-up visit to my clinic is required every half month to a month after surgery. This is until I tell the patient, “Your condition is stable and if you are not in any particular discomfort, you may not need to come back in the future”.