If the knee effusion is caused by trauma, if it is not a serious trauma, the effusion can be absorbed in 2-3 weeks after 2-3 weeks of braking and rest to reduce the activity, and the corresponding supportive symptomatic treatment can also be taken to achieve self-healing. If the knee effusion is caused by a more serious injury, without systematic treatment, the injury cannot be recovered and the cause of the effusion cannot be removed, the knee effusion will persist or even worsen, causing damage to the joint and resulting in serious dysfunction of the knee. For knee effusion due to injury, it is recommended that the patient go to the hospital for a detailed examination to clarify the diagnosis and then take rest and treatment according to the condition. In mild cases, the fluid can be absorbed by going home and resting with brakes and taking simple supportive and symptomatic treatment. If the injury is more severe, the knee joint fluid can only be slowly absorbed and the knee joint can return to normal after surgical treatment if necessary.