The sensation varies depending on how much fluid has accumulated in the knee. In cases of mild fluid buildup within the knee, it is often not noticeable. This is because under normal circumstances, there is a small amount of fluid in the knee joint. In the case of gradually increasing fluid accumulation, the knee joint will gradually swell and you will feel soreness and pain in the knee. This is especially true in cases of synovitis, because in synovitis, the synovial membrane secretes more synovial fluid, causing swelling of the knee joint. In the case of heavy fluid accumulation in the knee joint, diffuse swelling will form in the knee joint, the patella will float, and when you press the patella with your hand, it will feel as if the patella is floating on water, and the patella may sink under the pressure. At this time, it is usually necessary to carry out fluid extraction treatment of the knee joint, otherwise it will easily cause functional limitation of the knee joint.