Determination of the Typical Digital Infrared Thermographic Profile of the Knee of Distance Runners

Abstract

INTRODUCTION: Attempts have been made to use digital infrared thermal imaging (DITI) to identify or predict tissue injury in animals and humans. To date, limited data are available describing normal DITI profiles of human limb joints. PURPOSE: Our aim was to establish a normal DITI profile of the knee in pain-free collegiate distance runners. METHODS: Collegiate distance runners were assessed every two weeks over a three month cross-county season. At each visit, knee pain was rated bilaterally via the Nirschl Phase Pain Scale (NPPS), and anterior (A), posterior (P), lateral (L), and medial (M) DITI of each knee were recorded. Eight of 26 subjects (2 male, 6 female) experienced no pain in either knee during the season. Pain-free subject data were used to create a typical knee DITI profile. For each knee and view, temperature points within a standard area of observation were analyzed to determine mean, minimum (MIN), maximum (MAX), standard deviation (SD) and range (R). RESULTS: Individual data for each temperature variable were pooled across knees and over the season. One-way ANOVA and Fisher's LSD tests showed several significant between view differences. Mean temperature was greater for the P view compared to the A(p < 0.01) and M (p < 0.05) views. MIN temperature was greater for the P view compared to the other three views (p < 0.01). MAX temperature was lower for the A view compared to the other three views (p < 0.05). R was less for P and A views compared to L and M views (p < 0.01). Strong positive correlations (0.79 ≤r≤ 0.97) were found for mean and MAX temperature between all views. MIN, R, and SD showed strong positive correlations (0.75 ≤ r≤0.89)between A and L and M and L views, but the A and M views did not correlate as strongly (0.60 ≤ r ≤ 0.66). P views for MIN, R, and SD exhibited little correlation with the other three views (−0.18 ≤ r ≤ +0.28). CONCLUSIONS: While individual variations in knee temperatures among distance runners were noted, strong correlations for most measurements among views (A, P, M and L) suggest that as one view changed, temperatures in the other views changed similarly. These data help establish a normal DITI profile of the knee of distance runners, although further study is needed. These data may be used to determine whether relationships exist between changes in DITI profiles, knee pain and injury in distance runners.