# An app-based physical activity intervention for people with hip and knee osteoarthritis: protocol for the PIANISSIMO feasibility study

## TL;DR

This study tests a mobile app to help people with hip or knee osteoarthritis increase physical activity and improve their quality of life.

## Contribution

The study introduces a mobile app-based intervention tailored for osteoarthritis patients to promote physical activity adherence.

## Key findings

- The study will assess adherence to a 6-month app-based physical activity intervention.
- Acceptability and retention rates of the app will be evaluated through participant feedback and dropout rates.

## Abstract

Osteoarthritis is one of the most prevalent musculoskeletal disorders. In osteoarthritis patients, physical activity has been shown to be an effective tool to improve quality of life as well as to reduce the pain associated with the disease and the development of additional comorbidities. Yet osteoarthritis patients often do not meet the level of physical activity recommended to stay in good health. The PIANISSIMO study primarily aims to test the adherence of people with hip and knee osteoarthritis to a 6-month intervention for the promotion of physical activity specific to this population using a dedicated mobile app.

The PIANISSIMO study is a longitudinal, interventional feasibility study conducted through a dedicated mobile app. A total of 151 participants with hip or knee osteoarthritis will be included. The app will collect data and deliver the intervention. Data will be collected through questionnaires (i.e. demographic data, osteoarthritis history, sport history, pain and functional capacities, app evaluation) and from Apple Health/Google Fit apps. The PIANISSIMO study will use a 6-month physical activity intervention based on the Capability, Opportunity, Motivation–Behaviour change theory. Participants will receive a text notification on a daily basis; they will be asked to set their daily steps goal for the next week, and the mobile app will deliver feedback on daily step count and whether the goal of the week has been reached. The primary outcome of this study is the adherence (i.e. connection log and rate of answered questionnaires) to the app-based physical activity intervention. Retention will be calculated as the number of drop-outs over 6 months of follow-up. Moreover, the acceptability of the app and intervention by the study participants will be evaluated through a questionnaire.

This mobile app was designed to provide a digital solution for the promotion of physical activity in people with osteoarthritis. If the feasibility of delivering a physical activity intervention through the mobile app is confirmed, the efficiency of the tool in improving the quality of life of people with hip and knee osteoarthritis should then be properly investigated.

Registration number

NCT06385028 (https://clinicaltrials.gov/study/NCT06385028)

Protocol version 1.2

The online version contains supplementary material available at 10.1186/s40814-025-01744-z.