Infrared thermogram knee bone temperature reflects the severity of rheumatoid arthritis of the knee joint Purpose of the study: Infrared thermogram belongs to the category of functional imaging, where the microcirculation and thermal radiation style of the human body is influenced by inflammation, metabolism and regulated by sympathetic excitation and vasoactive substances. Changes in organ and blocked blood flow cause changes in local heat generation. Since blood flow and heat conduction from deep tissues to the body surface, thermograms can reflect the process of heat changes in the deep parts of the organism. The aim of this study: to find a standardized infrared thermographic measurement method, reproducible tests and to explore which distinct areas of the knee have the highest correlation of local temperature with the radiographic severity of OA. METHODS: This was part of a multicenter study with 15 control and 15 OA cases included in the study. the OA cases met the diagnostic criteria, x-ray KL grade 2-3, frequent pain in the past year, and medial joint space >2 mm. control group KL grade 0, no history of pain. X-rays and infrared thermograms of the relevant areas of the knee, including the medial, contralateral, knee, lower medial and lower contralateral areas, were measured. RESULTS: The mean temperature was similar in both groups (30.6°C), and skin temperature in the knee region of the OA group was significantly correlated with the severity of radiographic OA, p=0.02. The temperature of the kneecap was 30.1±1.05°C in patients with KL grade 2,and 30.5±1.14°C in patients with KL grade 3. DISCUSSION: Previous studies have shown that the surface temperature of the knee joint is closely related to the different X-ray stages of the knee joint. The surface temperature was higher in early stage OA, while in patients with OA at the most severe KL4 level of X-rays, the temperature of the knee joint was significantly lower. In this study, only the correlation between the temperature of different areas around the knee joint and the severity of the knee joint was observed. CONCLUSION: Temperature measured by infrared thermography is a reliable and objective method to reflect inflammation, and inflammation can reflect the severity of the knee joint as reflected by intrinsic K grading, therefore, the temperature of the knee joint kneecap can be measured to reflect the severity of knee injury.