Whether or not the knee effusion will go away depends on the amount of fluid.
There are many causes of knee effusion, such as synovitis, osteoarthritis, meniscus injury, can cause knee effusion, if a small amount of effusion through rest, hot compresses physiotherapy, slowly can be absorbed.
If the effusion is more, can not be completely absorbed through rest, you can use a sterile syringe to draw out the effusion, and then in the joint injection, pressure bandage, and at the same time take some oral medication to promote blood circulation and reduce the swelling of the treatment, most of them can also be absorbed.
If repeated knee joint effusion, fluid accumulation is more, this situation should also consider arthroscopic surgery to remove the diseased synovial membrane, repair the damaged tissue.
So whether the knee effusion can disappear by itself depends on the amount of fluid, a small amount of fluid can disappear.