PurposeTo compare the postoperative pain score, opioid consumption, and blood loss in knee osteoarthritis patients who underwent unilateral primary total knee arthroplasty with and without intraoperative cold solution irrigation.MethodIn total, 70 knee osteoarthritis patients were randomly included in the study and allocated into 2 groups. The first group was irrigated intraoperatively with a cold solution and the second group was irrigated intraoperatively with a room-temperature solution.ResultsThe cold solution group showed significantly lower pain scores (numerical rating scale, NRS) at 28 h postoperatively (p = 0.047). There were no significant differences in opioid consumption or blood loss between the groups.ConclusionsIntraoperative cold solution irrigation in unilateral primary total knee arthroplasty patients may provide the benefit of early postoperative pain reduction for up to 28 h but has no effect in terms of reducing opioid consumption or blood loss.Trial registrationThe trial was registered in the Thai Clinical Trials Registry (TCTR) Trial registration number ID: TCTR20200706001 on 06/07/2020.