Evaluation of a 12-week app-guided exercise intervention in patients with knee osteoarthritis (re.flex): a study protocol for a randomized controlled trial

Abstract Background Current health care demonstrates an insufficient provision and utilization of physical exercises despite their recommendation as a first-line treatment in clinical guidelines for patients with knee osteoarthritis (OA). Mobile health (m-health) technologies offer new opportunities to guide and monitor home-based exercise programs by using mobile devices and inertial sensors in combination with a digital application (app). This study will evaluate patient benefits resulting from the use of the specific digital health application re.flex for patients with knee OA. Methods This monocentric, two-arm, randomized controlled parallel-group trial will evaluate the effectiveness of the app- and sensor-guided exercise program re.flex for patients with moderate-to-severe knee OA. We aim to recruit 200 participants via newspapers, newsletters and information events. Participants will be randomly allocated to the intervention group and the control group in a 1:1 ratio. Participants in the control group will not receive any study intervention or instruction for any change to their previous health care utilization. Despite this, they are allowed to make use of usual care provided by their treating physician. The intervention group comprises a 12-week home training program with three sessions per week in addition to usual care. Exercises will be guided and monitored by use of the training app (re.flex) and two accelerometers that are attached proximally and distally to the affected knee joint. Pre- and postmeasurements will take place at baseline (t0) and after 12 weeks (t1). Primary outcomes will be osteoarthritis-specific pain and physical function measured with the Knee Osteoarthritis Outcome Score (KOOS) subscales Pain and Function in daily living (ADL). Second, further self-reported health outcomes, a performance measurement, app logfiles and safety will be assessed. Intervention effects will be calculated by baseline-adjusted analysis of covariance (ANCOVA) using an intention-to-treat approach. Multiple imputation will be applied. Discussion Re.flex can bridge part of the gap between recommendations for strengthening exercises in patients with knee OA and the insufficient actual care situation. This randomized controlled trial is designed to provide conclusions on the effectiveness of the health application re.flex for the population under study and will provide further insight into adherence rates and the safety of its use. Trial registration The trial was registered on 20/01/2023 at www.drks.de (ID: DRKS00030932).