Intra-articular temperatures of the knee in sports – An in-vivo study of jogging and alpine skiing

Background: Up to date, no information exists about the intra-articular temperature changes of the knee related to activity and ambient temperature. Methods: In 6 healthy males, a probe for intra-articular measurement was inserted into the notch of the right knee. Each subject was jogging on a treadmill in a closed room at 19 degrees C room temperature and skiing in a ski resort at -3 degrees C outside temperature for 60 minutes. In both conditions, temperatures were measured every fifteen minutes intra-articulary and at the skin surface of the knee. A possible influence on joint function and laxity was evaluated before and after activity. Statistical analysis of intra-articular and skin temperatures was done using nonparametric Wilcoxon's sign rank sum test and Mann-Whitney's-U-Test. Results: Median intra-articular temperatures increased from 31.4 degrees C before activity by 2.1 degrees C, 4 degrees C, 5.8 degrees C and 6.1 degrees C after 15, 30, 45 and 60 min of jogging (all p <= 0.05). Median intra-articular temperatures dropped from 32.2 degrees C before activity by 0.5 degrees C, 1.9 degrees C, 3.6 degrees C and 1.1 degrees C after 15, 30, 45 and 60 min of skiing (all n.s.). After 60 minutes of skiing (jogging), the median intra-articular temperature was 19.6% (8.7%) higher than the skin surface temperature at the knee. Joint function and laxity appeared not to be different before and after activity within both groups. Conclusion: This study demonstrates different changes of intra-articular and skin temperatures during sports in jogging and alpine skiing and suggests that changes are related to activity and ambient temperature.