One hundred patients undergoing total knee arthroplasty with drain placement at the end of surgery were randomized to either have the drain clamped for the first four postoperative hours, or to not undergo drain clamping. The purpose was to determine if there was a difference in blood loss between groups. Visible, hidden, and estimated blood losses were assessed up to 48 hours postoperatively. The results indicated that, despite significantly less blood drainage volume with the clamping protocol, total blood loss was estimated to be similar and there were no differences in rate of transfusion.