Introduction This protocol outlines the rationale, design and methods for the process and feasibility evaluations of the primary care management on knee pain and function in patients with knee osteoarthritis (PARTNER) study. PARTNER is a randomised controlled trial to evaluate a new model of service delivery (the PARTNER model) against a € usual care'. PARTNER is designed to encourage greater uptake of key evidence-based non-surgical treatments for knee osteoarthritis (OA) in primary care. The intervention supports general practitioners (GPs) to gain an understanding of the best management options available through online professional development. Their patients receive telephone advice and support for OA management by a centralised, multidisciplinary a € Care Support Team'. We will conduct concurrent process and feasibility evaluations to understand the implementation of this new complex health intervention, identify issues for consideration when interpreting the effectiveness outcomes and develop recommendations for future implementation, cost effectiveness and scalability. Methods and analysis The UK Medical Research Council Framework for undertaking a process evaluation of complex interventions and the Reach, Effectiveness, Adoption, Implementation and Maintenance (RE-AIM) frameworks inform the design of these evaluations. We use a mixed-methods approach including analysis of survey data, administrative records, consultation records and semistructured interviews with GPs and their enrolled patients. The analysis will examine fidelity and dose of the intervention, observations of trial setup and implementation and the quality of the care provided. We will also examine details of a € usual care'. The semistructured interviews will be analysed using thematic and content analysis to draw out themes around implementation and acceptability of the model. Ethics and dissemination The primary and substudy protocols have been approved by the Human Research Ethics Committee of The University of Sydney (2016/959 and 2019/503). Our findings will be disseminated to national and international partners and stakeholders, who will also assist with wider dissemination of our results across all levels of healthcare. Specific findings will be disseminated via peer-reviewed journals and conferences, and via training for healthcare professionals delivering OA management programmes. This evaluation is crucial to explaining the PARTNER study results, and will be used to determine the feasibility of rolling-out the intervention in an Australian healthcare context. Trial registration number ACTRN12617001595303; Pre-results.