First, it is caused by acute injury. Due to acute injury to the meniscus, local hemorrhage and hematoma can occur, as well as the corresponding acute inflammatory response, and local soft tissue can become congested and edematous, resulting in increased intra-articular exudate and effusion. Secondly, due to poor recovery from acute meniscal injury, the patient continues to move or exercise causing meniscal injury, resulting in aseptic chronic inflammation, which can also lead to persistent effusion in the knee joint. In this case, treatment and management should be carried out in both the acute and recovery phases to avoid persistent effusion in the knee joint. In the acute phase, rest and braking are required to promote the absorption of the effusion, and oral medications, topical medications and physical therapy can be used to achieve therapeutic results. During the acute phase, the effusion is reduced, so do not rush into activities, but brake and rest, and observe the absorption of the effusion. If you move too early or exercise too much when the symptoms are slightly relieved, the injury will be aggravated and the effusion will not heal, resulting in adverse sequelae to the knee joint.