The availability of hot compresses for knee effusion is related to its etiology, including bacterial infection, trauma, joint degeneration and other factors. If the effusion is caused by trauma, ice should be applied within 24 hours and hot compresses can be applied after 24-48 hours. The main purpose of hot compress is to promote local blood circulation and facilitate the absorption of fluid accumulation. Patients can usually use salt bags for hot compresses, or fried bran for hot compresses, twice a day for more than half an hour each time, which is more effective. In the case of localized septic arthritis resulting in fluid accumulation, hot compresses are not suitable and surgical treatment should be considered to flush and drain the localized fluid and provide anti-infection treatment. Patients are advised to reduce weight-bearing exercises during the treatment period to prevent aggravation of the disease, pay attention to the warmth of the knee, and at the same time, massage can be appropriate to strengthen the blood circulation in the leg.