Facilitating physical activity and reducing symptoms in patients with knee osteoarthritis: study protocol of a randomized controlled trial to test a theory-based PrevOP-psychological adherence program (PrevOP-PAP)

Background: The present randomized controlled trial, which is crossed with the "PREVenting the impairment of primary Osteoarthritis by high impact long-term Physical exercise regimen" Main Medical Trial (PrevOP-MMT), aims to evaluate a psychological adherence program (PrevOP-PAP), and is designed to support persons with knee osteoarthritis (OAK) in the uptake and maintenance of regular physical activity to reduce OAK symptoms. The PrevOP-PAP is based on the Health Action Process Approach (HAPA), a social-cognitive theory predicting health behavior change in individuals, extended here by social network characteristics and social exchange processes. It is expected that participants with OAK receiving the PrevOP-PAP will maintain higher levels of regular physical activity throughout a 24-month period and consequently report lower levels of OAK symptoms than participants of an active control condition. Methods: A total of N = 240 participants with medically verified moderate OAK will be randomly assigned to an intervention condition (PrevOP-PAP-I; 50%) or an active control condition (PrevOP-PAP-CTRL). The PrevOP-PAP-I includes a motivational intervention, repeated self-regulation interventions, and a network creation intervention delivered over 12 months. Modes of intervention delivery include a paper-pencil motivation leaflet with a quiz, a computer-assisted face-to-face intervention, four computer assisted phone-based interventions, and activity calendars. The PrevOP-PAP-CTRL includes the motivational intervention only. Primary outcome will be OAK symptoms. Secondary outcomes include objectively and subjectively measured physical activity and indicators of quality of life. Other outcomes are HAPA-derived self-regulatory indicators as well as proposed social network and social exchange mechanisms of health behavior change. Assessments take place at baseline, 6 months, 12 months, 18 months, and 24 months following baseline. Discussion: Based on the extended HAPA, this study seeks to reveal the self-regulatory and social mechanisms of the uptake and maintenance of physical activity and their relation to disease symptoms in persons with OAK. The design and evaluation of this program are intended to become a yardstick for future development and implementation of digitalized psychological adherence programs in this population.