The presence of a fever in the knee is likely to be a sign of inflammation of the knee joint. There may be aseptic inflammation or septic arthritis due to bacterial infection. Therefore, blood tests, MRI of the knee joint, and rheumatoid immune factor should also be checked. First of all, if the inflammation is aseptic, it is likely to be a rheumatoid immune system disease that is causing the fever in the knee, that is, aseptic inflammation. This could be rheumatoid arthritis, ankylosing spondylitis, or other psoriasis causing a fever in the knee. Often the appropriate anti-rheumatic medication needs to be chosen for the specific type of disease, in addition to the possible use of hormones for treatment. Secondly, if there is an obvious bacterial infection causing the inflammation of the knee, it is more effective to use antibiotics for intravenous drip treatment. Again, if the fever is accompanied by a temperature of more than 38.5 degrees, antipyretic medication, such as ibuprofen suspension, may be required.