24 patients scheduled for total knee arthroplasty were randomized to surgery completed with either the use of patient specific instrumentation (PSI; Trumatch, DePuy) or conventional instrumentation. Patients were primarily assessed for hemoglobin (Hb) drop from postoperative day 1 to postoperative 5, while secondary outcomes included blood loss to postoperative drainage, incidence of transfusion, and operative and tourniquet times. While Hb drop did not significantly differ between groups on PODs 1-3, Hb drop on POD5 was smaller in the PSI group compared to the conventional group. Otherwise, no significant differences were reported for postoperative blood loss to drainage, incidence of transfusion, and operative and tourniquet times.