Kong DY, Oh JH, Choi WR, et al. - This study was undertaken to investigate how effective epinephrine is on postoperative clinical in primary total knee arthroplasty(TKA). Researchers enrolled a total of 116 cases (89 patients) who had undergone primary TKA and were randomized into two groups depending on whether epinephrine was mixed. Patient-controlled analgesia using fentanyl was initiated immediately after the operation. They postoperatively analyzed 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 did not have any impact on postoperative acute pain control and opioid usage.