Water on the knee does not always need to be removed. It takes time and treatment to reduce the pain and swelling.
Water on the knee is also called knee effusion. It is caused by arthritis or an injury to the area. Avoiding any sudden movements and protecting the joint when playing sports such as soccer or football can prevent the knee effusion from occurring. Putting ice on the knee and elevating the leg can reduce the swelling, and over-the-counter pain medication can ease the pain. In more serious cases, a doctor may have to aspirate the joint to remove the fluid buildup.