Trajectories of physical activity following digital education and exercise therapy—a longitudinal registry study among 15,197 persons with knee or hip osteoarthritis

Abstract Objective This study examined trajectories of physical activity (PA) and associated factors among individuals with knee or hip osteoarthritis (OA) participating in a digital education and exercise therapy program. We additionally compared patterns of patient-reported outcomes (PROs) across the identified trajectories. Methods A longitudinal registry-based study. Individuals aged 40 + years with a diagnosis of knee or hip OA—confirmed through referral documentation or based on the National Institute for Health and Care Excellence (NICE) guidelines and Swedish national criteria— participating in the digital program with responses to validated self-reported PA questions at enrolment and at least one follow-up (3-month intervals up to 1 year after enrolment) were included ( n  = 15,197). The recommended PA level was defined as ≥ 150 min/week of moderate to vigorous physical activity (yes/no). We used group-based trajectory modelling (GBTM) to identify distinct PA trajectories and multinomial logistic regression to explore associated factors. Changes in PROs from enrolment up to 1-year follow-up across PA trajectories were analysed using random intercept models. Results The proportion of participants reaching the recommended PA levels rose from 51.4% (95% CI: 50.6, 52.2) at enrolment to 58.5% (57.1, 59.9) at one year. GBTM identified four distinct PA trajectories: persistently high (41.2%), persistently low (30.4%), increasing (16.5%), and declining (11.9%). Body mass index (BMI) followed by physical function were the most important factors associated with PA trajectory. All PA trajectories experienced clinically comparable improvements in PROs. Conclusions About 60% of participants reached or maintained recommended PA levels. The results suggest possible PA promotion by targeted strategies for individuals with higher BMI and poorer function. Comparable improvements in PROs across PA trajectories may support the provision of education and exercise therapy to all individuals with OA regardless of their PA level.