Abstract Purpose For patients with end-stage knee osteoarthritis, joint replacement is a widely used and successful operation to help improve quality-of-life when non-operative measures have failed. For a significant proportion of patients there is a choice between a partial or total knee replacement. Decision aids can help people weigh up the need for and benefits of treatment against possible risks and side-effects. This study explored patients’ experiences of deciding to undergo knee replacement surgery to identify information priorities, to inform a knee replacement decision aid. Methods Four focus groups were held with 31 patients who were candidates for both partial and total knee replacement surgery. Two focus groups included patients with no prior knee replacement surgery (pre-surgery); two with patients with one knee already replaced and who were candidates for a second surgery on their other knee (post-surgery). Data were analysed using Framework Analysis. Results Participants described a process of arriving at ‘readiness for surgery’ a turning point where the need for treatment outweighed their concerns. Referral and personal factors influenced their decision-making and expectations of surgery in the hope to return to a former self. Those with previous knee surgery offered insights into whether their expectations were met. ‘Information for decisions’ details the practicality and the optimal timing for the delivery of a knee replacement decision aid. In particular, participants would have valued hearing about the experiences of other patients and seeing detailed pictures of both surgical options. Information priorities were identified to include in a decision aid for knee replacement surgery. Conclusions Patients’ experiences of surgical decision-making have much in common with the Necessity-Concerns Framework. Whilst originally developed to understand drug treatment decisions and adherence, it provides a useful lens to understand decision-making about surgery. The use of a decision aid could enhance decision-making on knee replacement surgery. Ultimately, patients’ understanding of the risks and benefits of both surgical options could be improved and in turn, help informed decision-making. The knee replacement decision aid is perceived as a useful tool to be associated with other detailed information resources as recommended.