The right measure for the right question: A framework for domain-matched patient-reported outcome measure selection in knee arthroplasty research

Patient-reported outcome measures (PROMs) are one of the primary tools for evaluating outcomes in knee arthroplasty research. Yet, they are frequently selected by convention rather than scientific rationale. The available instruments differ substantially in their measurement domains, spanning joint-specific symptoms and perception, physical function and activities of daily living, sport-specific and high-demand function, health-related quality of life, and patient satisfaction and expectation. When the domain of the chosen PROM does not correspond to the domain addressed by the research question, clinically meaningful differences may go undetected, producing false-negative results. This problem is further compounded by floor and ceiling effects that vary between instruments and follow-up timepoints, and by minimal clinically important difference thresholds that are PROM-specific, population-specific, and may be set unrealistically high for comparative studies between two effective surgical interventions. This editorial proposes a domain-matched approach to PROM selection in knee arthroplasty research and presents a practical framework assigning a first-choice instrument, acceptable alternatives, and supplementary measures to five clinical research domains: mechanical aspects of surgery, treatment selection and operative indication, early postoperative recovery, revision arthroplasty outcomes, and long-term outcomes in standard and high-demand patients.