A small amount of fluid in the knee usually takes one month to recover. Knee effusion is usually caused by knee injuries and synovitis secondary to osteoarthritis of the knee causing synovial hyperplasia. Depending on the degree of knee swelling, mild swelling is considered to be less severe inflammation, and recovery time for this condition is about one month. If there is damage to the meniscus or ligaments of the knee joint and there is fluid and blood accumulation in the joint, it will take a longer time to absorb the fluid and it will take 6-8 weeks to fully recover. In addition, you can also take oral medication such as synovitis pellets as prescribed by your doctor. Usually, after a month, the fluid in the knee joint can be slowly absorbed and return to normal. In conclusion, after the development of knee effusion, the first thing to do is to keep the knee joint warm, reduce knee joint activities, and avoid strenuous exercise.