Proper analgesia after total knee arthroplasty (TKA) is important for encouraging early
ambulation, which can facilitate improved patient outcomes and early hospital discharge. For
pain control after TKA, adductor canal blocks (ACBs) improve upon the gold standard femoral
nerve blocks (FNBs) since they do not cause as much quadriceps muscle weakening, while
providing equivalent analgesia. Multimodal analgesia has become commonplace as a method of
superior pain control with fewer side effects. Magnesium sulfate as an adjuvant to FNB local
anesthetics can improve pain control after surgery; however, it also prolongs time to
ambulation. There are no reports on the effect of magnesium sulfate in ACBs on analgesia
after TKA. Thus the purpose of this randomized, double-blind, controlled trial is to
determine whether magnesium sulfate given with local anesthetics via ACB can prolong
analgesia, reduce pain scores and opioid consumption, and increase mobilization in TKA
patients.