Validity and reliability of a smartphone application for self-measurement of active shoulder range of motion in a standing position among healthy adults

Shoulder range of motion (ROM) is one of the most important indicators of shoulder disease severity, function, and physical assessment. A universal goniometer (UG) was used as a gold standard for ROM measurement. Recently, smartphone applications for ROM measurement have attracted attention as alternatives to UG. This study aimed to investigate the validity and reliability of active ROM measurements using a smartphone application goniometer that can be used by patients in a standing position. The dominant shoulders of 19 healthy participants were included in the study. The 2 observers who were physical therapists used the UG, whereas the participants used a smartphone application goniometer to measure the shoulder ROM. A recorder, who is a physical therapist independent of the observer and participant, read and recorded the shoulder ROM measurements. The order of the measurement movements and devices used was randomized. Agreement between the smartphone application goniometer and UG (percentage of participants for whom the difference between the UG and application measurements was within ±20% of the mean of the goniometer and application measurements) ranged between 42% and 100%. The intraclass correlation coefficient values (3, 1) for the agreement between the smartphone application goniometer and UG was between 0.72 and 0.97, showing significant and approximately perfect correlations. High agreement with the UG showed excellent validity, indicating that the smartphone application goniometer used by the participants in the standing position is an excellent method and instrument. The results suggest a simpler, more reliable, practical, and inexpensive method for measuring ROM required for telerehabilitation.