Ab. No. 89 Reproducibility of a Smartphone-Based Application for Assessing Knee Range of Motion

Introduction:Smartphone applications using in-built gyroscope chips are attractive options that can facilitate self-assessment of knee range of motion without having to wear a sensor-based device.Methods:A cross-sectional study was conducted to compare this smartphone-based app with universal goniometer (UG) in assessing active knee range of motion in sitting and lying position. Consecutive patients with knee osteoarthritis or those who had knee replacement or the healthy accompanier and hospital staff above 18 years of age and consenting to volunteer were approached for the study at a tertiary care academic hospital in India. The comparisons were repeated measurements with UG and test-app under same conditions, UG versus test-app, physiotherapist versus patient’s accompanier with test-app in the same phone, in different phones, and a physiotherapist measuring on different stool heights using test-app. We report mean difference between two measurements with 95% limits of agreement and intraclass correlation coefficient (ICC) calculated using one-way random effects.Result:The 95% LoA between the UG and test-app in supine flexion was -7.5° to +4.5° and extension was ±4°. The test retest 95% LoA of the test-app in supine flexion and sitting flexion across all scenarios was within ± 8.5°. The test-retest 95% limits of agreement of extension in sitting and supine position across all scenarios was within ±6.5°. Test-retest reliability (ICC) of knee flexion ranged between 0.70 to 0.99 and extension between 0.16 to 0.97 across all scenarios.Conclusion:The smartphone-based app is reliable to differentiate between various ranges of motion of knee with measurement errors no greater than universal goniometer. This app has the potential to measure changes in ROM that are above 8° of flexion and above 7° in extension.This app can enhance the ability to remotely measure and monitor knee ROM of pathologic knee.