A Multicomponent Mobile Health Intervention to Reduce Sedentary Time After Knee Replacement: Randomized Controlled Trial (Preprint)

BACKGROUND Total knee replacement (TKR) is a common surgery for end stage knee osteoarthritis. Although reductions in pain and improvements and mobility occur after surgery, physical activity levels often do not change. Given the challenges of increasing physical activity in this population, targeting reductions in sedentary behavior may be a first step; however, no prior studies have examined the feasibility and effects of a sedentary reduction intervention after TKR. OBJECTIVE This study examined the effects of a 2-month multicomponent mHealth sedentary reduction intervention on sedentary time in adults with TKR. METHODS Adults (65.3 ± 9.4 years, 32.7±6.9 kg/m2, 74.7% female, 77.1% white) with a TKR ≤1 year ago were randomized to NEAT!2 (n=42) or an attention-matched control group (n=41). The NEAT!2 intervention focused on reducing sedentary time via a smartphone app designed to interrupt prolonged bouts (≥30 min) of sedentary behavior and 5 coaching calls emphasizing goal setting and problem solving. The control group focused on surgery recovery via an app/website and 5 educational calls. Multiple linear regression models with generalized estimating equation (GEE) examined intervention effects and differences between groups at each time. RESULTS Retention was 96% and 95% at 2 and 5 months, with no differences between groups. NEAT!2 participants completed 4.95±0.2 calls, used the app on 40.3±13.8 days (out of 56 days), and received an average of 9.6±6.0 notifications/day. The NEAT!2 intervention did not result in significant effects on any of the study’s outcomes at 2 or 5 months and no differences were observed between groups. However, more days of using the app was associated with greater increases in moderate-to-vigorous intensity physical activity (r = 0.335, 95% CI 0.017, 0.585, p= 0.037). CONCLUSIONS This study highlights the challenges of reducing sitting time in adults with TKR. Future studies should explore alternative behavior change techniques across different levels of influence (e.g., environmental, social) in future interventions within the first year after TKR. CLINICALTRIAL NCT04482400