Background: Exercise is a core treatment for older adults with knee pain yet within clinical trials its beneficial effects can be small and reduce over time. This may be due to non-adherence to the exercise programmes. The attitudes, beliefs and behaviours of older adults may influence exercise adherence, as may the attitudes and beliefs and practice behaviour of physiotherapists prescribing the exercise. At present little is known about these issues. Methods: A systematic review was completed to identify previous interventions aimed at improving adherence to exercise for older adults with knee pain. Two mixed methods investigations utilising surveys and interviews were completed with a community sample of older adults with knee pain and a national sample of physiotherapists to explore their exercise attitudes, beliefs and behaviours. The findings were used to develop recommendations targeting patients, physiotherapists, and the wider healthcare system about how to optimise adherence to physiotherapy-led exercise for older adults with knee pain. Results: The systematic review identified 24 studies, of which 8 successfully enhanced exercise adherence. Successful interventions included use of specific adherence enhancing strategies, supervision of exercise and supplementing exercise programmes with additional instruction and prompts. Surveys and interviews revealed that overall, levels of physical activity amongst older adults with knee pain were low and there was uncertainty about the benefits of exercise, whether it was safe, and what to do when exercising in the presence of pain. Physiotherapists reported delivering exercise in ways that were sub-optimal in terms of enhancing adherence, likely influenced by their own uncertainties about the role of exercise for knee pain and service pressures. Conclusion: The exercise attitudes, beliefs and behaviours of older adults and of physiotherapists, and wider healthcare system factors are important issues to address when attempting to enhance adherence to physiotherapy-led exercise for older adults with knee pain.