The purposes of this study are to investigate the effect of the cold air application in the skin and intraarticular temperature changes and to observe the rebound temperature changes after cooling. We recorded the changes of the skin surface and intraarticular temperatures of knees during and after the cold air application. The intraarticular temperature was measured by a temperature probe inserted into the knee joint cavity and the skin temperature by the infrared system. Eighteen healthy subjects were examined. The knee was cooled by a 5-minutes application of CRAis (Kyung-won Century, Korea) machine and the intraarticular and skin temperatures of knees were measured at every 0.5-minute during and after the cold therpy, then at every minute for 5 minutes, and every 5-minute for the next 110 minutes. We also evaluated the variables that might affect the skin and intraarticular temperature changes. Results showed that the mean skin temperature dropped from 31.8oC to 10.5oC immediately after the cold air application for 5-minutes. The mean intraarticular temperature dropped from 33.9oC to 30.0oC after the cold air application for 5-minutes. Two hours after the initiation of treatment with cold air, the mean intraarticular temperatures did not recover to the baseline values(p<0.01). No significant correlations were found between the body mass index with the intraarticular and surface temperatures of knees. A highly significant correlation was noted between the baseline skin surface and intraarticular temperatures(p<0.01). In conclusion, the reduction of the joint temperature by the cold air application using CRAis machine can be a useful treatment method for the synovitis of knees.