OBJECTIVE: Reduced knee confidence is common in people with knee osteoarthritis (OA) and is likely to influence how people with knee OA engage with movement and activities. However, there is conflicting evidence surrounding the association between confidence and function. This may be because knee confidence has been assessed via a single questionnaire item that was not developed for people with knee OA and thus may not provide an accurate or comprehensive assessment of confidence in this population. A better understanding of knee confidence could inform a more thorough assessment of the construct both in clinical and research contexts. Therefore, the aim of this study was to explore the meaning of knee confidence from the perspective of people with knee OA. METHODS: Fifty-one people with a clinical diagnosis of knee OA took part in a one-to-one semistructured interview. Interviews explored how each participant conceptualized knee confidence. Reflexive thematic analysis was selected as a flexible approach for identifying patterns of meaning across cases through a combination of data-driven and theory-informed coding of the transcribed data. RESULTS: People with knee OA conceptualized confidence with reference to 1 or more of 4 themes: (1) symptoms, (2) functional ability, (3) the internal structure of the knee, and (4) knowledge about knee OA and its management. Each conceptualization of confidence was associated with present and future concerns. CONCLUSION: Because people with knee OA conceptualize knee confidence in different ways, a single-item measure is unlikely to capture all of the aspects of this construct in this population. This may explain the conflicting evidence around the association between reduced knee confidence and function in people with knee OA. IMPACT: This study showed that a multi-item measure is needed to measure knee confidence in people with knee OA. Clinicians and researchers need to understand what knee confidence means to people with knee OA, because it is likely to influence how these individuals engage with movement and activities. Understanding this relationship can enable more targeted education and functional rehabilitation for people with knee OA.