Intra-Articular Knee Temperature Changes

Abstract

Background Cryotherapy is commonly applied without research documenting the intra-articular (IA) temperature changes or subject discomfort between ice and a cryotherapy device. Hypothesis The null hypothesis is that no difference would be observed in IA temperature decline or subject tolerance between ice and the cryotherapy device in normal knees. Study Design Prospective, within-subject controlled clinical trial. Methods Twelve subjects had IA temperature in suprapatellar pouch and skin recorded bilaterally after application of cryotherapy versus ice. Subject tolerance was recorded by 10-cm visual analog scale (VAS). Statistical evaluation was by Spearman's correlation analysis and paired, nonparametric Wilcoxon's signed rank test. Results Both significantly lowered (P < 0.001) skin and IA temperature with median decreases (ice/cryotherapy) at 30 (3.3 °C/2.2 °C), 60 (12.8 °C/7.1 °C), and 90 (15.2 °C/9.7 °C) minutes. However, ice lowered the IA temperature significantly more than the cryotherapy device (P < 0.001) and was more painful by VAS at 30 and 60 minutes (P < 0.01). Conclusions Both methods produced large declines in skin and IA temperatures. However, ice was more effective yet resulted in higher pain scores. The authors hypothesize that IA temperatures below a threshold are associated with increased perceived pain.