One-Month Postoperative Pain Predicts 3-Month Postoperative Dissatisfaction in Total Knee Arthroplasty Patients

The purpose of this study was to evaluate the relationship between 1-month pain scores and 3-month postoperative satisfaction and investigate whether an immediate postoperative pain score cutoff exists between satisfied and dissatisfied patients.

This was a secondary analysis of a multicenter, longitudinal, cohort study comprised total knee arthroplasty (TKA) patients (n = 1763) using a digital care management platform. Pain was assessed at 1 month postoperatively through an 11-point numeric rating scale (NRS). Satisfaction was assessed at 3 months postoperative through the Knee Society composite satisfaction score (KSS). Patients were stratified into satisfied (KSS >30) and dissatisfied (KSS <30) subgroups. Quantile regression was used to create a best-fit line to identify a cutoff between the 1-month NRS and the 3-month KSS. A logistic regression model was used to classify patients as satisfied or dissatisfied that included comorbidities, 1-month active flexion range of motion, anxiety/depression score, sex, age, and body mass index. The importance of the features in the model was assessed using permutation importance method to create a best-fit line between satisfaction and NRS.

The 1 month mean NRS and satisfaction scores were 3.7 ± 2.0 and 29.4 ± 8.6, respectively. A total of 621 patients (35.2%) were dissatisfied at 3 months postoperatively. A moderate correlation was found between 1-month NRS pain and 3-month satisfaction (r = -0.39, P < 0.001). Based on the best-fit line, the cutoff for dissatisfaction occurs with an NRS for pain of >4.0. The model achieves an area under curve (AUC) of 0.73 (SD = 0.02), with a maximum f1-score of 0.65, corresponding to sensitivity = 0.87 and specificity = 0.44.

One-month postoperative pain scores greater than 4.0 were associated with patient dissatisfaction at 3 months postoperatively. Assessing pain in the immediate postoperative period can provide clinicians with diagnostic data that may help detect patients at risk for a poor prognosis 3 months following TKA.