Accuracy of a Smartphone Software Application Compared With a Handheld Goniometer for Measuring Shoulder Range of Motion in Asymptomatic Adults

BACKGROUND: Typically, shoulder range of motion (ROM) measurements are performed in a clinic setting, where physicians, physical therapists (PTs), and occupational therapists make use of a goniometer. PURPOSE: To determine the accuracy of a smartphone-based ROM software application (app) in assessing active shoulder ROM and compare the measurements with traditional goniometry as measured by a PT. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: This prospective, nonblinded study was conducted at a single institution with adult asymptomatic participants with full active ROM of both shoulders. Participants were enrolled between June 1 and 15, 2021. Each participant self-assessed their active shoulder ROM using the PeerWell smartphone app. A single PT concurrently measured each participant’s active shoulder ROM using a handheld universal goniometer. Bilateral shoulder ROM (forward flexion, abduction [AB], external rotation, internal rotation [IR], and extension) was measured 2 times for each participant. Interrater reliability between the smartphone app and PT measurements as well as intrarater reliability for each method of measurement were assessed using the intraclass correlation coefficient (ICC), and limits of agreement were analyzed for the difference in measurement methods. RESULTS: Data were analyzed for 60 shoulders (30 right, 30 left) from 30 participants (mean age, 31.4 ± 11.7 years; 73% female). The interrater reliability between the 2 methods was excellent for all movements (ICCs, 0.90-0.96). For all movements except shoulder AB, the mean difference in the measurements between the 2 methods was <1.3°; the mean difference in AB ROM was 2.08°. For all movements except IR, both PTs and the app showed excellent intrarater reliability (ICCs >0.90); for IR, good intrarater reliability (ICC ≥0.75) was observed. CONCLUSION: The PeerWell smartphone app provided measurements comparable with manual measurements taken by a PT using a goniometer. These data provide evidence that the smartphone app is a reliable and valid tool for measuring shoulder ROM and show promise for measuring and monitoring patient ROM remotely.