Whether to apply hot or cold compresses to a swollen knee needs to be decided on a case-by-case basis. Part of the treatment should be cold compresses and part of the treatment should be hot compresses, as follows: 1. Part of the treatment should be cold compresses: If the knee is traumatized, cold compresses should be used in the initial stage to eliminate swelling and relieve pain. In the later stage, it can be changed to hot compress treatment to accelerate the swelling to subside. 2. Some of them should be treated with hot compress: If the swelling is caused by chronic diseases of the knee joint, such as arthritis and synovitis, hot compress treatment can be used to improve the blood circulation of the synovial membrane and promote the swelling of the joint to subside. Therefore, the cause of the swelling of the knee joint should be clarified first, and then decide whether to choose cold compress treatment or hot compress treatment according to the cause. The correct choice will lead to significant improvement of clinical symptoms, while the wrong choice may instead aggravate the symptoms of knee swelling and affect the recovery of the knee joint.