When redness, swelling, heat and persistent joint pain occur after joint replacement, the possibility of infection should be considered. Infections after joint replacement are generally categorized into three types according to the time of occurrence: early postoperative infections, delayed infections and late infections. The clinical manifestations of infections occurring at different times are different. 1. Early postoperative infection: acute postoperative infection, occurring within 3 months after the operation, with purulent secretion, usually with fever with pain, reduced range of limb movement, redness and swelling of the limb, which needs to be cleaned up and washed out and drained in a timely manner. 2. Delayed infection: It occurs half a year to 2 years after surgery. The most common clinical manifestation is persistent joint pain, which is characterized by static pain, tension, dull pain and fever. 3. Late infection: occurs 2 years after surgery. Patients usually have had surgery, tooth extraction, upper respiratory tract infection or distant infection in the recent past. Physical examination reveals limited active and passive movement of the joints, pain in the joints caused by internal and external rotation, and swelling of the joints with redness, heat or pressure pain around the joints. When the above symptoms occur after arthroplasty, we should be alert to the possibility of infection, and need to go to the hospital in time for follow-up.