Validity and intra-rater reliability of the clinometer application for ankle dorsiflexion assessment: a practical solution for android users

INTRODUCTION: Accurate assessment of ankle dorsiflexion (ADF) range of motion (ROM) is crucial for identifying and managing lower limb dysfunctions. Smartphone-based inclinometer applications (Apps) offer a cost-effective and accessible alternative to traditional tools but remain underexplored on Android devices. OBJECTIVE: To evaluate the validity and intra-rater reliability of the Clinometer App on Android smartphones for measuring ADF ROM during the weight-bearing lunge test (WBLT). MATERIALS AND METHODS: ADF ROM was measured in 50 limbs from 25 healthy adults using both a universal goniometer and the Clinometer App on a Samsung A55 smartphone during the WBLT. Two sessions were conducted one week apart. Pearson’s correlation assessed concurrent validity; intra-rater reliability was determined using intraclass correlation coefficients (ICC[3,3]), standard error of measurement (SEM), and minimal detectable change (MDC95). Agreement was evaluated via Bland-Altman analysis. RESULTS: The Clinometer App demonstrated very high concurrent validity with the goniometer (r = 0.97), excellent intra-rater reliability (ICC = 0.93), low SEM (1.25º), and acceptable MDC95 (3.47º). Bland-Altman plots showed minimal bias (-0.48º) and narrow limits of agreement (-2.82º to +1.85º). CONCLUSION: The Clinometer App is a valid, reliable, and accessible tool for measuring ADF ROM during the WBLT in healthy adults. Its use may enhance musculoskeletal assessment efficiency, particularly when applied by trained clinicians under standardized protocols, and holds promise for broader App in clinical and remote monitoring contexts.