Kong DY, Oh JH, Choi WR, et al. - This study was undertaken to investigate whether and how effective epinephrine is on postoperative clinical outcomes in primary total knee arthroplasty (TKA). Researchers recruited a total of 116 cases (89 patients) who had undergone primary TKA. Patients were assigned randomly into 2 groups depending on whether epinephrine was mixed. They postoperatively examined numerical Rating Scale, the cumulative dose of fentanyl, active range of motion of the knee joint, and wound complications. After TKA, the use of epinephrine in periarticular injection applying ropivacaine did not have any impact on postoperative acute pain control and opioid usage.