Prepare ice bag: a large plastic bag from the supermarket, filled with 600ml-800ml of water, placed in ice, the ratio of ice to water is about 1:1, the amount of the above ice and water mixture can be adjusted according to the size of the knee joint. Tighten the bag and try to exclude the air inside the pocket, so that the ice bag is easy to fit. Ice area: the injury site and about 2-3 cm of skin on the periphery. Painful areas during mobility exercises during the rehabilitation period must be incorporated into the ice pack. Note: ice pack and skin with a towel between (patients with wounds, can be in the case of smooth wound healing (doctor’s judgment), retain 2 layers of dressing plus 1 layer of plastic wrap moisture-proof instead of towel); in general, joint injuries or post-operative rehabilitation exercises each ice pack lasts about 20 minutes, the first ice pack may have to last 25-30 minutes, so that the entire injury site will feel “cool through”; need to be reminded that the skin ice pain lasts 5 minutes to stop the ice to prevent frostbite; 40-60 minutes between ice packs. Mild injury (less bruising, swelling is not obvious) can be iced 3-5 times; severe injury (more bruising, swelling is obvious) need to increase to 6-8 times. Contraindications to ice: large tissue damage, infectious shock, skin bruising, ice should not be used to prevent tissue necrosis. Cold compress should not be used behind the occiput, auricle, scrotum, etc. to prevent frostbite; abdomen should not be iced to prevent intestinal spasm or diarrhea; patients with coronary artery disease with hyperthermia should avoid foot ice compress to prevent angina caused by transient coronary artery constriction.