The main purpose of this project is to promote physical activity in patients with osteoarthritis. More specifically, this study aims to test the acceptability of an app to promote physical activity in the target population, and consequently the feasibility of such an approach.

A mobile phone application - namely PIANISSIMO - will be developed specifically for this project. It aims to spread knowledge on the benefits of physical activity and collect data on how this knowledge can induce behavior changes toward a more physically active lifestyle.

The intervention is delivered via the app, which will send daily notifications on physical activity and sedentary behavior, and ask the participants to set their weekly goal (i.e., daily steps). The app will also collect daily steps count and ask the participant to fill in questionnaire on pain once a week.

Osteoarthritis patients will be recruited from the general population living or working in Luxembourg.

The PIANISSIMO study is a feasibility pilot study. Thus, it is a single-group study, with the participants being their own controls. 150 participants with osteoarthritis will be included. For this study, a mobile application will be developed. It will include self-administered questionnaires, allow physical activity data collection, and deliver the intervention (goal setting, data feedback, notifications to the user and self-completion questionnaires). The intervention will last 6 months, with a further 6-month follow-up.

After signing the explicit consent and data protection notice, participants will encode data and information about individual and chronic pain characteristics, sport history, general health status: Individual questionnaire will include demographic data and general health status. The osteoarthritis pain questionnaire focuses on disease history and evaluation that will include a SF-WOMAC questionnaire. In order to deliver the same intervention for every participant, sham notifications will be send the first week, until the next Sunday for the first goals to be set. First real notification will be send the first Monday after the registration to the study.

The daily step count will be collected in background during the whole study. Then the intervention will be delivered though the phone application: each week, the participant will define a new daily step goal for the following week. Then he/she will receive daily notifications (except Sundays) about physical activity, sedentary behaviour and their consequences on general health and osteoarthritis specifically.

He/she will also be asked to fill in a pain questionnaire once a week. The participant can also spontaneously notify pain at any moment in the same questionnaire. At the end of each month, the participant will be asked about her/his functional status with the WOMAC-SF questionnaire.

At the end of the 6-month intervention, a questionnaire will be sent to the participant to evaluate the application.

During the 6-month follow-up, daily step count will still be collected in background, and pain questionnaires will be sent twice a month, but without any intervention delivered.

Inclusion Criteria:

• Osteoarthritis patients, living or working in Luxembourg
• Signed informed consent form
• Adequate understanding of one of the study languages (English, French, or German)
• Stated willingness to comply with the study procedure consisting in completing the surveys and the digital physical activity intervention

Exclusion Criteria:

• Rheumatoid arthritis