Real-time data capture

A subset of participants participated in RTDC as a supplementary and exploratory addition to the qualitative interviews. Patients were recruited on a voluntary basis; the first 10 patients to register interest in both the concept elicitation interviews and RTDC were included in the RTDC subset. These patients downloaded an app to their personal smartphone/tablet and completed a total of 14 tasks over a 7-day period. The app was designed for this study and tailored to collect qualitative and quantitative data relevant to the study objectives. Qualitative tasks were sent at different times throughout each day and were designed to explore symptoms of HOA as they were happening and their impact on different domains of HRQoL (e.g. physical functioning, daily activities) (Supplementary Table S1). Participants responded by submitting images or self-recorded audio or video content via the app. In addition, each morning, participants were also asked to rate the severity of specific symptoms: pain on a 0–10 numerical rating scale, stiffness on a 5-point verbal rating scale (none, mild, moderate, severe and extreme), and swelling on a 5-point verbal rating scale. App responses were sent remotely to a secure database.