Inter-rater reliability and validity of angle measurements using smartphone applications for weight-bearing ankle dorsiflexion range of motion measurements

The purpose of this study was to examine the inter-rater reliability, validity, and error of angle measurements for ankle dorsiflexion range of motion while in the weight-bearing position using a smartphone application. Reliability and validity study. Measurement positions were performed by one experienced examiner. Eighteen volunteers participated in the study. Three examiners (examiner 1 and examiner 2 had completed the course to become qualified certified athletic trainers and examiner 3 did not belong to the course) performed smartphone application measurements. Ankle dorsiflexion range of motion was measured in the lunge position. Radiographic measurements were performed using a bony landmark. The markerless method for application measurements was used, using a body part as a landmark. Using the markerless method for application measurements, the intra-class correlation coefficients were 0.945. Using Pearson's correlation coefficient and intra-class correlation coefficients to compare the radiographic measurements and markerless method for application measurements, three examiners showed very high correlation (r > 0.9) and almost perfect (>0.81) intra-class correlation coefficient. Error values were less than 5° according to examiner 1 and examiner 2. Smartphone application measurements using the markerless method of ankle dorsiflexion range of motion exhibited inter-rater reliability and high validity. •Reliability and validity of ankle ROM measurements have not been established.•This study examined the inter-rater reliability and validity of ankle dorsiflexion ROM.•Smartphone app measurements of ankle dorsiflexion ROM had reliability and validity.•App measurements for examiner having knowledge were only small measurement errors.