If there are no other uncomfortable symptoms, it is generally normal. If accompanied by swelling, pain and other symptoms, it may be due to rheumatoid arthritis, septic arthritis and synovitis and other reasons. 1. Normal situation: if the patient does not exercise for a long time, suddenly after strenuous exercise may appear knee fever, usually do not need special treatment, rest for a period of time can be recovered on their own. 2. Rheumatoid arthritis, septic arthritis: If the patient’s knee fever is accompanied by obvious redness, swelling, pain and wandering pain, it may be caused by rheumatoid arthritis or septic arthritis. 3. Synovitis: If there is a history of trauma or cumulative injury to the knee, symptoms of synovitis may occur, and after exercise, obvious redness, swelling, fever and other phenomena will often occur. To summarize, if the patient after exercise in addition to knee fever and no other obvious symptoms, can not do special treatment, but if accompanied by other symptoms of discomfort, should go to the hospital in a timely manner to avoid delaying the condition.