Generally, knee effusion can be healed in 1-3 months, as follows: 1. Minor symptoms: If the knee effusion is a small amount, caused by trauma and strain, the patient can promote the rapid absorption of the effusion through rest, braking, and exercise of the muscles around the knee, and the effusion will generally subside completely in about a month, and the patient can resume normal life and work. 2. Moderate or above: For moderate or above Knee joint effusion is usually slow to recover after conservative treatment, and usually takes about three months to fully recover. 3. Other: Patients with knee meniscus injury have difficulty recovering from knee joint effusion even after conservative treatment, and need to undergo minimally invasive arthroscopic surgery to treat the initial lesion, suture the meniscus, and restore the function of the meniscus before knee joint effusion can gradually recover in about three months. Therefore, the recovery time of knee effusion needs to be determined by different etiologies, and early treatment can lead to complete recovery of the effusion.