Predicting Pain in Total and Partial Knee Arthroplasty

Object: Although pain relief is a primary goal of a total knee arthroplasty (TKA) and partial knee arthroplasty (PKA), a significant number of arthroplasty patients experience unexplained pain. This study attempts to determine preoperative or intraoperative factors that may predict pain after knee arthroplasty. Methods: 2585 primary TKAs and 423 PKAs were performed between 1993 and 2013. Infections, loosening, and revision arthroplasty were excluded. Knee Society scores, demographics, component sizes, preand postoperative alignment, treatment of the posterior cruciate ligament, range of motion, and diagnosis were analyzed. Statistical analysis utilized repeated measures ANOVA. Results: Significant predictors of increased pain after TKA were preoperative varus alignment >5 ̊ (p = 0.0042), postoperative flexion range of motion <105 ̊ (p < 0.0001), postoperative flexion contracture >5 ̊ (p = 0.0006), small tibial component sizes (p = 0.0080), excision of the posterior cruciate ligament (p = 0.0259), and diagnosis as osteonecrosis (p = 0.0077). Factors not associated with pain included age, body mass index, gender, postoperative alignment and bone quality. For PKA, age was the only factor associated with pain. Conclusions: Six factors were found to be relevant to postoperative pain in TKA. For PKA, reported pain is not associated with any of the same factors, but is associated with age. Surgeons should be aware of these risk factors as we continue to understand pain after total and partial knee arthroplasty.