Fever in the ankle often has to be considered for several reasons, including joint sprain, synovitis, skin disease, infection, etc., as follows: First, joint sprain: there may be an acute sprain of the ankle joint, so that there will be subcutaneous bleeding, redness, swelling and fever. Second, synovitis: it may be present in the acute attack of synovitis of the ankle joint or in the acute attack of osteoarthritis of the ankle joint, in which there will be redness, swelling, heat and pain of the joint, and it will also be accompanied by diffuse pressure pain of the joint. Third, skin diseases: Consider skin diseases around the ankle joint, such as localized skin eczema, which can cause redness and swelling of the skin around the ankle joint and is accompanied by obvious itching. Fourth, infection: It may be related to septic infection of the ankle joint, especially when the chronic osteomyelitis of the ankle joint has an acute attack, it will cause redness, swelling, heat and pain of the ankle joint.