Synovitis of the knee is a complex disease, so when it recovers depends mainly on the cause, age and also the condition: 1. Generally speaking, synovitis of the knee in young adults is mainly due to trauma, and the accumulation of blood and fluid in the knee joint will occur after the injury. It will recover through conservative treatment rest or physical therapy for 2-4 weeks; 2. In elderly knee arthritis synovitis, the main cause is progressive cartilage degeneration and recurrent inflammation of the synovial membrane, resulting in increased joint fluid, the cause is more complex and lasts longer, so the symptoms will alternate. The recovery time is not easy to determine; 3. Simple synovitis is caused by repeated strain, so this kind of synovitis will appear repeated accumulation of fluid, enlargement, generally after rest are easy to improve, but after strain symptoms appear again; 4. Infectious factors, synovitis is more common is tuberculosis, the course of the disease will be more prolonged, even after conservative treatment, 9-18 months to basically control, so the time will be It takes 9-18 months to basically control, even after conservative treatment, so it takes longer.