Preoperative factors associated with failure to achieve the minimal clinically important difference in quality of life following total knee arthroplasty.

BACKGROUND: The patient characteristics and preoperative factors that affect the Knee Injury and Osteoarthritis Outcome Score (KOOS) quality of life (QOL) after total knee arthroplasty (TKA) remain unclear. Therefore, we aimed to determine patient characteristics and preoperative risk factors associated with the lack of the minimal clinically important difference (MCID) in the KOOS QOL subscales 1 year after TKA. METHODS: This single-center cohort study included 149 patients with knee osteoarthritis who underwent primary TKA using the subvastus approach. Patients were divided into two groups based on whether they achieved or failed to achieve the 1-year postoperative MCID in KOOS, in reference to the preoperative baseline score. RESULTS: Fifty-four patients did not achieve the MCID in the KOOS QOL scales 1 year after TKA. Significant predictors included in univariate analysis included the preoperative prevalence period, knee flexion range of motion (ROM), and KOOS pain, activities of daily living (ADL), and function in sports and recreation (Sport/Rec). Multivariate logistic regression analysis identified knee flexion ROM as the most significant factor (odds ratio: 1.080; 95% confidence interval: 1.048–1.112; P = 0.001). According to the receiver operating characteristic curve, a preoperative knee flexion ROM of 120° was the threshold for predicting achieved MCID in the KOOS QOL 1 year postoperatively (sensitivity: 0.61; specificity: 0.86); the area under the curve was 0.81. CONCLUSIONS: Patients with longer preoperative prevalence periods and higher preoperative KOOS pain, ADL, and Sport/Rec scores were more likely not to achieve the MCID in the QOL. Furthermore, limited preoperative knee flexion ROM may affect the risk of not achieving the MCID.