Remote follow-up after total knee arthroplasty: validity of patient-reported outcome measures as a triage tool – a prospective cohort study

Background: Routine in-person review after total knee arthroplasty (TKA) is costly and resource-intensive. Whether remotely-collected patient-reported outcome measures (PROMs) can reproduce the clinician’s follow-up decision-not merely correlate with it-is unknown. We assessed the agreement and triage accuracy of three PROMs against the clinician-administered knee society score (KSS), and whether comorbidity should modify follow-up. Methods: In this prospective cohort of 96 patients undergoing primary TKA for osteoarthritis, the Oxford knee score (OKS), Western Ontario and McMaster universities osteoarthritis index (WOMAC), short form (SF)-36 and KSS were recorded preoperatively, at 3 weeks and at 1 year. Agreement was assessed by Bland-Altman analysis, triage accuracy by ROC analysis against a clinician-defined suboptimal outcome (lowest-quartile 1-year KSS), and predictors by multivariable regression. Results: Data were complete for all 96 patients (mean age 66.1 years; 72.9% comorbid; no loss to follow-up). All instruments improved by 1 year (p<0.001). Despite high PROM-KSS correlations (1-year OKS r=0.96), Bland-Altman analysis showed systematic disagreement (WOMAC bias +19.9 standardised points), so the instruments are not interchangeable. A remote OKS <28 identified the suboptimal outcome with area under the curve 0.98, sensitivity 100%, specificity 93%, negative predictive value 100% and kappa 0.88, missing no affected patient. Comorbidity count independently predicted poor outcome (adjusted odds ratio 4.0 per comorbidity, p<0.001); 1-year KSS fell stepwise across strata (p<0.001). Conclusions: After the 3-week visit, a normal remote OKS reliably excludes a poor clinician-defined outcome, supporting a comorbidity-stratified hybrid pathway: remote follow-up for low-risk patients and in-person review for high-risk patients. External, longer-term validation is required.