The burning sensation without pain in the knee may be caused by the physiological phenomenon of strenuous exercise, or it may be caused by synovitis, aseptic inflammation and other diseases. 1. Physiological phenomenon: when the exercise is too strenuous or exercise time is too long, it will prompt the whole body to accelerate blood circulation, resulting in the body to emit a lot of heat, so there is no pain in the knee, but there is a burning sensation of the phenomenon, generally a normal physiological phenomenon, generally can be relieved after rest. 2. Disease factors (1) synovitis: after synovitis occurs, there is usually fluid inside the knee joint, the absorption process of the fluid and the process of inflammation reaction, which will cause a feverish reaction, so the knee will have a burning sensation. (2) Aseptic inflammation: When the knee is overworked or cold, aseptic inflammation of the knee may occur due to irritation. After the occurrence of sterile inflammation, the inflammatory factor is constantly stimulated, so the knee will produce a burning sensation. However, since there is no pathogenic microorganisms infecting sterile inflammation, it usually does not produce pain or pain is not intense at the initial stage. There are different reasons for the burning sensation in the knee without pain, so it is recommended that the patient should consult a doctor for timely examination to clarify the specific cause of the disease and then follow the doctor’s instructions for treatment.