Ointment can be applied to knee joint effusion. When knee joint effusion occurs, topical ointment can be used to activate blood circulation, relieve swelling and pain, and warm the meridians and channels. However, patients need to be aware that the external treatment of ointment is only an adjunctive treatment for knee effusion. Although a series of symptoms can be relieved after the application of ointment, such as relief of knee pain and swelling, this type of external treatment does not have any effect on the underlying pathological changes of knee effusion. In knee effusion, the underlying pathology is aseptic inflammation within the joint and synovial hyperplasia, both of which cannot be treated by applying creams. Patients who have knee effusion must first go to an orthopedic department of a level II or higher hospital for consultation and then do regular treatment. For example, treatment with non-steroidal drugs, or arthroscopy for intra-articular cleaning, on top of which the ointment can be supplemented to deal with the related complications.