Is there a Threshold Preoperative WOMAC Score That Predicts Patient Satisfaction after Total Knee Arthroplasty?

The aim of this study was to identify threshold preoperative Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores that were predictive of patient dissatisfaction 1 year after total knee arthroplasty (TKA). A retrospective cohort of 3,324 patients undergoing a primary TKA was identified from an established arthroplasty database. Patient demographics, comorbidities, and the WOMAC score were collected preoperatively. Patient satisfaction was assessed at 1 year using four questions that focused on: overall outcome, activity, work, and pain. Receiver operating characteristic (ROC) curve analysis was used to identify threshold values predictive of dissatisfaction. The overall satisfaction rate at 1 year was 89.7% ( n =2982). Patients who were satisfied had a significantly greater preoperative pain (3.6, 95% confidence interval [CI] 1.6-5.6, p <0.001) and functional (4.5, 95% CI 2.6-6.5, p <0.001) component and total (4.2, 95% CI 2.3-6.0, p <0.001) WOMAC scores compared with those who were dissatisfied. ROC curve analysis demonstrated the preoperative pain ( p =0.001) and functional ( p <0.001) components and total ( p <0.001) WOMAC scores were significant predictors of satisfaction. Patients scoring<36 for the pain and function components and<35 for the total WOMAC score were more likely to be dissatisfied with their overall outcome, but the area under the curves (AUCs) for these predictive threshold values were 0.56, 0.54, and 0.60, respectively, indicating poor prognostic value. A similar finding was observed for satisfaction with pain relief and ability to work and recreational activities; however, in addition the stiffness component was also a significant ( p <0.001) predictor with a threshold value of<43. Again, these thresholds were of poor prognostic value with an AUC of less than 0.57 for all these satisfaction questions. Threshold values in the preoperative component and total WOMAC scores were not reliable prognostic indicators of overall patient satisfaction or for satisfaction with pain relief, ability to do work, or recreational activities after TKA.