Passive knee angles were measured in fixed positions for 40 knee joints (20 subjects). Two registered physical therapists, one novice and one experienced, conducted the measurements. Both registered physical therapists were blinded to the measurements throughout the study.
The results showed very good intrarater (intraclass correlation coefficient [ICC] 0,997-0,998, standard error of mean 1.15-1.48, smallest detectable difference [SDD] 3.19-4.09, limits of agreement -3.36-3.04, -4.66-4.09) and interrater reliability (ICC 0.994, standard error of mean 2.11, SDD 5.85, limits of agreement -4.75-6.95) for measurements of knee joint ROM. No statistical difference between a novice and an experienced assessor was detected (p = 0.86).
The results of the present study showed very good ICC values for both intrarater and interrater reliability measuring knee joint ROM with EasyAngle. Relatively high SDD values were seen for both assessors and may indicate a problem monitoring small differences between measurements. Further studies are recommended to increase the generalizability of the results.