Association Between Three-Month Patient-Reported Outcomes and One-Year Recovery After Total Knee Arthroplasty: A Prospective Cohort Study

(1) Background: Early patient-reported outcome measures (PROMs) may identify suboptimal recovery after total knee arthroplasty (TKA). This study examined whether differences between early outcome groups persisted at 12 months and whether the three-month Oxford Knee Score (OKS) was independently associated with the 12-month OKS. (2) Methods: In this prospective, single-centre observational cohort study, 416 patients undergoing primary TKA were assessed using the OKS, EuroQol-5D, and the EndoCert Risk Score at three and 12 months. Four groups were defined by three-month clinical examination findings (satisfactory versus requiring further attention) or, without examination, by three-month OKS (<29 versus ≥29). In 358 patients with complete data, a multivariable general linear model examined the adjusted association between the three- and 12-month OKS. (3) Results: Mean OKS improved in all four groups. Patients with unfavourable early outcomes had lower mean 12-month OKS than those with favourable early recovery. In the adjusted model, the three-month OKS was associated with the 12-month OKS (B = 0.78, 95% CI 0.68–0.87; p < 0.001), whereas follow-up status was not (p = 0.614). (4) Conclusions: The three-month OKS was associated with the 12-month OKS, without establishing validated individual prediction. Group differences did not preclude further improvement. The contribution of follow-up interventions could not be determined.