Predictors associated with failing to achieve a patient-acceptable symptom state in the Oxford Knee Score following total knee arthroplasty

AIM: To define the Patient-Acceptable Symptom State (PASS) in the Oxford Knee Score (OKS) following total knee arthroplasty (TKA) and identify independent preoperative factors associated with failure to achieve this threshold. METHODS: A retrospective cohort of 3304 patients undergoing primary TKA who completed preoperative and 6-month OKS was identified from an arthroplasty registry. The PASS was defined using receiver operating curve analysis, using patient satisfaction at 6 months as the anchor. Regression analysis was used to identify independent preoperative predictors of achieving the PASS. RESULTS: The PASS was defined as OKS ≥31 (area under the curve [AUC] 0.865, 95% CI 0.850-0.881) with 2333 (70.6%) patients achieving this. Patients not achieving a PASS were younger, had a higher BMI, and worse baseline PROMs (all p < 0.001). Higher preoperative OKS (odds ratio [OR] 1.09 per point) and EQ-VAS (OR 1.01 per point) were independently associated with achieving a PASS (both p < 0.001). A preoperative OKS ≤19 was associated with achieving a PASS (AUC 0.707). PASS achievers were more likely to be satisfied (OR 15.3, p < 0.001), though 54.4% of non-achievers were also satisfied. CONCLUSION: The PASS was defined as ≥31 points in the OKS at 6 months following TKA. Lower preoperative OKS and EQ-VAS scores were associated with failure to achieve this threshold. While PASS attainment was associated with patient satisfaction, 54% of those not achieving a PASS were still satisfied, highlighting a limitation of this PROM threshold in isolation. LEVEL OF EVIDENCE: Retrospective study, Level III.