Our findings support the hypothesis that the pain relief and opioid-sparing effect are enhanced by the addition of preemptive dexamethasone to the multimodal analgesic regimen. Patients who received dexamethasone experienced lower pain and consumed less opioid during the 6- to 24-hour postoperative period compared with patients who received ramosetron alone. These findings agree with those of two recent studies that showed that 125 mg of methylprednisolone reduced resting pain for 2 to 48 hours and reduced opioid consumption for the first 24 hours in 24 patients who had unilateral TKA [38], and that 300 mg hydrocortisone reduced postoperative pain and epidural medication for the first 24 hours in 17 patients who had bilateral TKAs concurrently treated with a multimodal analgesic regimen [24] (Table 4). Our results and those of previous studies [24, 38] suggest that incorporation of corticosteroids in a multimodal analgesic regimen provides synergistic analgesia and opioid-sparing effects. We noted that pain occurring between 6 and 24 hours after surgery may be breakthrough pain from local anesthetics included in the periarticular injection. A temporary increase in pain during 12 to 24 hours after surgery has been observed with multimodal regimens that involve periarticular injection, regardless of the surgery type or concomitant analgesic regimen [27–30, 37].We believe the addition of dexamethasone to the current multimodal analgesic regimen after TKA may have potent analgesic effects in combating breakthrough pain caused by components of the multimodal regimen.