Background <p>Frailty is common in patients undergoing joint replacement, with approximately 20–25% of patients having moderate-severe frailty. In an orthopaedic context, frailty is associated with increased mortality, longer hospital stays, post-operative complications, more hospital admissions, and worse pain and function after surgery. Multimodal prehabilitation may improve outcomes for frail patients undergoing joint replacement, however evaluation of the effectiveness of this approach is needed. Prior to conducting a randomised controlled trial (RCT), a feasibility study can address key uncertainties and explore how to optimise trial design and delivery. The aim of this qualitative study embedded within a randomised feasibility study was to gain an understanding of the experiences of older frail patients waiting for a total hip replacement (THR) or total knee replacement (TKR) participating in a multimodal prehabilitation programme, and to seek insight into the barriers and facilitators influencing adherence.</p> Methods <p>This was a qualitative study embedded within a randomised feasibility study of a 12-week daily home-based prehabilitation programme (exercise and protein supplements) for frail patients aged ≥ 65 years on the waiting list for primary THR or TKR. Participants in the feasibility study were invited to participate in a semi-structured qualitative interview. Interview questions were informed by a topic guide, and an inductive thematic analysis of interview transcripts was conducted.</p> Results <p>Interviews were conducted with 10 participants randomised to the intervention group. Three overarching themes that influenced adherence to the prehabilitation programme were identified. Intervention design factors included the intervention appointment and telephone support, provision and clarity of written information and tailoring of the exercise programme. Internal factors included pain, general health and wellbeing, and personal motivations and perceived value. Environmental/external influences included social influences and daily life (integration, interruption and changes to usual routine).</p> Conclusions <p>This qualitative study identified multifactorial barriers and facilitators that influence frail older adults’ adherence to multimodal prehabilitation before joint replacement. Our findings also highlight the importance of provision of tailored prehabilitation and additional support and resources to optimise accessibility and adherence.</p> Trial registration <p>ISRCTN11121506, registered 29 September 2022.</p>