Predictors Associated with Failing to Achieve a Patient Acceptable Symptom State (PASS) in the Oxford Knee Score (OKS) following Total Knee Arthroplasty (TKA)

Title : Predictors Associated with Failing to Achieve a Patient Acceptable Symptom State (PASS) in the Oxford Knee Score (OKS) following Total Knee Arthroplasty (TKA)

Abstract:

Aim: To define the Patient Acceptable Symptom State (PASS) in the Oxford Knee Score (OKS) following Total Knee Arthroplasty (TKA), and to identify independent preoperative factors associated with failure to achieve this threshold.

Methods: A retrospective cohort study that included patients who underwent primary TKA during an 8-year period was undertaken. A total of 3,304 patients completed both preoperative and 6-month postoperative OKS. The PASS was defined using Receiver Operating Characteristic (ROC) curve analysis, with patient satisfaction at 6 months as the anchor. Logistic regression was performed to identify independent preoperative predictors of achieving the PASS.

Results: A threshold of ≥ 31 points in the OKS was identified as the PASS (AUC 0.865, 95 % CI 0.850–0.881), of which 70.6% patients achieved this. Patients failing to achieve a PASS were younger, had a lower BMI, and worse baseline Patient Reported Outcome Measures (PROMs) (all p < 0.001). A pre-operative OKS ≤ 19 was associated with non-achievement of PASS (AUC 0.707), while higher pre-operative 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). Those attaining a PASS were more likely to be satisfied with their TKA (OR 15.3). Nevertheless, 54.4 % of patients below the PASS threshold still reported being satisfied with their TKA.

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 closely correlated with satisfaction, 54% of those not achieving a PASS were still satisfied, highlighting the need for individualised interpretation of outcome measures. Level of evidence: Retrospective study, Level III.

Keywords: Oxford knee score, PASS, Knee, Arthroplasty, Satisfaction

Biography:

Steve Robins is a third-year medical student at the University of Sunderland with a strong interest in orthopaedic surgery and outcomes research. He has contributed to several orthopaedic projects, including a systematic review and registry-based analysis, and leads clinical audits within the Orthopaedic department at Sunderland Royal Hospital. Steve also founded his university’s orthopaedic society and is actively involved in academic teaching and event coordination. With a growing academic portfolio, he plans to apply for Core Surgical Training with a focus on trauma and orthopaedics. This project represents his first first-author submission for presentation and publication.