Effect of Postoperative Medication on Range of Motion After Total Knee Arthroplasty: An Evaluation of Venous Thromboembolism Chemoprophylaxis

INTRODUCTION: Postoperative stiffness is a common complication after total knee arthroplasty (TKA), leading to limited range of motion (ROM), pain, and reduced function. Direct oral anticoagulants (DOACs), such as factor Xa inhibitors, are commonly prescribed for venous thromboembolism (VTE) prophylaxis but may increase the risk of postoperative stiffness due to postoperative bleeding within the knee. This study seeks to evaluate the effect of postoperative VTE prophylaxis (factor Xa inhibitors vs. aspirin) on ROM outcomes in patients undergoing TKA. METHODS: A total of 1,054 patients who underwent primary TKA by the senior author between November 2021 and May 2023 were retrospectively identified from an institutional database. Records were examined at preoperative, 2-week, 6-week, 1-year postoperative visits. Logistic regression models analyzed ROM outcomes, defining success as 90° flexion and 0° extension at 2 weeks and 125° flexion and 0° extension at 6 weeks. Manipulation under anesthesia (MUA) was recorded as a secondary end point. RESULTS: Factor Xa inhibitors (apixaban or rivaroxaban) did not significantly affect ROM success at 2 weeks (OR = 0.956, 95% confidence interval [CI, 0.866 to 1.054], P = 0.364) or 6 weeks (OR = 0.986, 95% CI [0.892 to 1.089], P = 0.778) postoperatively, compared with aspirin. VTE prophylaxis type was not found to be significantly associated with MUA likelihood. DISCUSSION: No association was found between postoperative ROM and VTE prophylaxis medication. Previous studies used lower ROM thresholds or focused solely on MUAs. Understanding the effects of DOACs on postoperative stiffness can help guide chemoprophylaxis decisions after TKA.