After a patient has suffered a knee sprain, it is important to apply cold rather than hot packs as soon as possible. After a period of time, such as 48 hours after the injury, the patient can gradually change to hot compresses. After the patient’s knee sprain, local internal bleeding and aseptic inflammation may appear rapidly, at this time, we should use cold compresses as soon as possible to reduce the bleeding and inflammation. If hot compresses are applied at this time, it may lead to more serious bleeding from the ruptured small blood vessels, which will aggravate the injury. After a period of time, that is, after 48 hours, the local bleeding has basically stopped, then you need to switch to hot compresses to promote the local absorption of bruises and the decline of inflammation.