Objective To elicit perspectives of family physicians and patients with knee osteoarthritis (KOA) on KOA, its treatment/management and the use of a mobile health application (app) to help patients self-manage their KOA.Design A qualitative study using Cognitive Task Analysis for physician interviews and peer-to-peer semistructured interviews for patients according to the Patient and Community Engagement Research (PaCER) method.Setting Primary care practices and patient researchers at an academic centre in Southern Alberta.Participants Intentional sampling of family physicians (n=4; 75% women) and patients with KOA who had taken part in previous PaCER studies and had experienced knee pain on most days of the month at any time in the past (n=5; 60% women).Results Physician and patient views about KOA were starkly contrasting. Patient participants expressed that KOA seriously impacted their lives and lifestyles, and they wanted their knee pain to be considered as important as other health problems. In contrast, physicians uniformly conceptualised KOA as a relatively minor health problem, although they still recognised it as a painful condition that often limits patients’ activities. Consequently, physicians did not regard KOA as a condition to be proactively and aggressively managed. The gap between physicians’ and patients’ conceptualisation of KOA and its treatment extended to the use of an app for self-management. While patients were supportive of the app, physicians were sceptical of its use and focused more on accountability and patient resources.Conclusions The clear discord between physicians’ mental models and patients’ lived experience and perceived needs around KOA emphasised a gap in understanding and communication about treatment and management of KOA. As such, this preliminary and formative research will inform a codesign approach to develop an app that will act as a communications tool between patients and physicians, enabling patient–physician discussions regarding modifiable self-management options based on a patient’s perspectives and needs.