Intra-articular knee temperature changes: ice versus cryotherapy device.

Abstract

Cryotherapy is commonly applied without research documenting the intra-articular (IA) temperature changes or subject discomfort between ice and a cryotherapy device. 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. Prospective, within-subject controlled clinical trial. 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. Both significantly lowered (P < 0.001) skin and IA temperature with median decreases (ice/cryotherapy) at 30 (3.3 degrees C/2.2 degrees C), 60 (12.8 degrees C/7.1 degrees C), and 90 (15.2 degrees C/9.7 degrees 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). 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.