Concurrent validity and reliability of the Simple Goniometer iPhone app compared with the Universal Goniometer

Abstract

Objectives: The aim of this study was to assess the concurrent validity and reliability of the Simple Goniometer (SG) iPhone® app compared to the Universal Goniometer (UG). Design: Within subject comparison design comparing the UG with the SG app. Setting: James Cook University, Townsville, Queensland, Australia. Participants: Thirty-six volunteer participants, with a mean age of 60.6 years (SD 6.2). Interventions: Not applicable. Main outcome measure: Thirty-six participants performed three standing lunges during which the knee joint angle was measured with the SG app and the UG. Results: There were no significant differences in the measures of individual knee joint angles between the UG and the SG app. Pearson correlations of 0.96–0.98 and intraclass correlation coefficients of 0.97–0.99 (95% confidence interval: 0.95–1.00) were recorded for all measures. Using the Bland–Altman method, the standard error of the mean of the differences and the standard deviation of the mean of the differences were low. Conclusion: The measurements from the SG iPhone® app were reliable and possessed concurrent validity for this sample and protocol when compared to the UG.