Hot compresses for knee effusion can be applied as follows: hot water bags or salt bags can be used on the knee joint, keeping the temperature at 38-40°C to avoid skin burns due to high temperature, and the skin surface should be separated by a towel. Hot compresses should be applied to the front, inside and outside of the knee joint, avoiding the back of the knee joint, i.e. the popliteal fossa, where there are important neurovascular passages and thin skin that can easily cause injury. The knee joint should be kept straight during the hot compressing process, preferably with the static contraction of the quadriceps muscle, which can accelerate the absorption of the knee joint effusion.