Predictors of pain following total knee arthroplasty

Although total knee arthroplasty (TKA) has provided dramatic improvements in function and pain for the majority of patients with end-stage knee arthritis, recent studies have demonstrated that 15-20% of patients report persistent pain and dissatisfaction with their results. The purpose of this prospective cohort study was to determine which preoperative characteristics predict moderate to severe movement and resting pain at 6-months post TKA using a comprehensive set of physiological and psychological variables. 215 preoperative TKA patients had multiple demographic variables recorded, completed psychological questionnaires assessing anxiety, depression, and pain catastrophizing, underwent quantitative sensory testing and scored pain intensity at rest and with knee range-of-motion (ROM) on a 0-20 numeric rating scale. At 6-months, pain intensity ratings were scored again. Predictors were determined by multivariate logistic regression analyses. Patients with severe knee ROM pain prior to TKA had a 10x higher odds of moderate to severe ROM, relative to none or minimal pain, at 6 months. A second model was fitted to identify other explanatory variables of persistent ROM pain in addition to preoperative ROM pain, which found trait anxiety as the only other variable to be significant with an odds ratio of 1.4. Whilst depression, anxiety and pain catastrophizing have been demonstrated in prior studies to predict poor outcomes following TKA; we have demonstrated a simple test of pain intensity with active ROM preoperatively as an overriding predictor of persistent pain at 6 months following TKA. If these findings are corroborated in larger studies, strategies to address this particular patient group may improve overall satisfaction rates of TKA.