Clinical reliability and usability of smartphone goniometers for hip range of motion measurement

[Purpose] This study aimed to utilize the objective measurements and a survey questionnaire for assessing the intra- and inter-rater reliability, measurement time, and usability of a smartphone application type of goniometer to measure the hip joint angles. [Participants and Methods] Three examiners (physiotherapists) measured the hip joint range of motion using universal and smartphone goniometers on 30 daycare center rehabilitation patients. Reliability was calculated using the intra-class correlation coefficient. The examiners completed a questionnaire survey for assessing the usability of the goniometers. [Results] The intra-rater reliability was high, but the inter-rater reliability was low. Measurement times using the two instruments showed no difference. The usability questionnaire findings suggested that the smartphone goniometer was easier to use than the universal goniometer. [Conclusion] Reliability within the raters was high, but reliability among the raters was low. However, both goniometric devices provided a satisfactory range of motion measurement data when a single evaluator used the same device for all measurements.