The reliability and minimal detectable change of shoulder mobility measurements using a digital inclinometer

The present study investigated the intrarater reliability, interrater reliability and minimal detectable change at the 90% confidence interval (MDC₉₀) of active shoulder range of motion measurements using digital inclinometry. Two investigators each measured two repetitions of active flexion, abduction, external rotation (ER), and internal rotation (IR) on the nondominant shoulder of 30 asymptomatic participants in a blinded repeated measures design. Results indicated good intrarater reliability with Intraclass Correlation Coefficients (ICCs) (3, k) of Flexion=0.83, Abduction=0.91, ER=0.94 and IR=0.87. Interrater ICC values (2, k) were moderate to good with Flexion=0.58, Abduction=0.95, ER=0.88 and IR=0.93. The MDC₉₀ for the interrater analysis indicated that a change of equal to or greater than 8° (Flexion), 4° (Abduction), 8° (IR), and 9° (ER) would be required to be 90% certain that the change is not due to intertrial variability or measurement error. Digital inclinometry appears to be a reliable instrument for quantifying normal shoulder mobility when strict measurement protocols are adhered to. Clinicians and researchers should consider the MDC values presented when interpreting change values during subsequent measurement sessions.