Background: Measuring subtalar joint (STJ) motion is accompanied by complications due to the oblique STJ axis which results in triplanar pronation and supination.
Objective: We developed a pronator and supinator testing apparatus whose axis was aligned with Inman's STJ axis. The purpose of this study was to assess day-to-day reliability of active STJ range of motion (ROM) measurements and to compare the results with those of a rearfoot goniometer.
Methods: Active pronation, supination and total STJ ROM measurements were administered to 12 men (mean age: 23.8 years) and 12 women (mean age: 22.3 years) at two separate test sessions. Intraclass correlations (ICC), limits of agreement (LoA) and minimum detectable change (MDC) were calculated.
Results: Except for pronation ROM in men, the STJ goniometer revealed substantial (ICC > 0.8) reliability in all conditions. Relative MDCs and LoAs were below 15% and 10%, respectively. Significantly higher total ROM (P< 0.05) was found for women compared to men when using the STJ goniometer. The rearfoot goniometer showed high reliability (ICCs > 0.7) but underestimated STJ ROM in average of 37%.
Conclusions: Both goniometric methods showed high day-to-day reliability. However, when using the rearfoot goniometer, researchers have to consider whether the level of underestimation of STJ motion is acceptable in the context of the planned investigation.
Keywords: Range of motion; intraclass correlations; limits of agreement; minimum detectable change; pronation; subtalar joint axis; supination.