Intra-articular knee temperature changes - Ice versus cryotherapy device

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 A temperature with median decreases (ice/cryotherapy) at 30 (3.3degreesC/2.2degreesC), 60 (12.8degreesC/7.1degreesC), and 90 (15.2degreesC/9.7degreesC) 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.