Purpose: To understand patients' and physical therapists' perspectives related to decision making during outpatient rehabilitation after total knee arthroplasty (TKA), and to describe potential barriers and opportunities for shared decision making (SDM) in this setting. Methods: A qualitative study examined the beliefs, thoughts, and experiences of patients and physical therapists regarding decision making in outpatient rehabilitation after TKA. Semi-structured interviews were conducted and analysed using directed content analysis. Results: Thirty-five participants were interviewed (20 patients, 15 physical therapists). Three main themes emerged from the data: (1) there is variability among physical therapists in how patients are involved in care decisions, (2) several features of the outpatient care paradigm are not supportive of SDM, and (3) preoperative patient-clinician interactions may facilitate SDM in postoperative rehabilitation, but these interactions are not typically utilized. Conclusion: Physical therapists described using decision-making strategies with varying levels of patient involvement. Both patients and physical therapists described barriers to routine use of SDM in the outpatient setting. Several actionable strategies for overcoming these barriers were identified for providers and organizations seeking to consistently use SDM in outpatient TKA rehabilitation.