【Abstract】 Objective To study the influence of close-box and open-box knee prosthesis on postoperative bloodloss in patients undergoing total knee replacement(TKR). Methods From June 2005 to December 2006, 108 atients with primaryknee osteoarthritis were treated with TKR. Closed-box knee prosthesis was used in 54 patients (Group A), including unilateral(Group A1, n =27)and bilateral (Group A2, n =27). There were 7 males and 47 females, aged 41-76 years; and the diseasecourse was 4-16 years. Open-box knee prosthesis was used in 54 patients(Group B), including unilateral (Group B1, n =27)andbilateral(Group B2, n =27). There were 8 males and 46 females, aged from 59-81 years; and the disease course was 8-26 years. Thepostoperative blood loss and perioperative blood loss were compared between groups. Results The postoperative blood losswas (890±352), (1 694±528), (1 068±386) and(2 065±622) mL in groups A1, A2, B1 and B2, respectively. There was no significantdifference between groups A1 and B1(P gt; 0.05). There was significant difference between groups A2 and B2(P lt; 0.05). The totalblood loss was (1 095±329), (2 082±594), (1 274±415) and (2 459±734) mL in groups A1, A2, B1 and B2, respectively. Therewas no significant difference between groups A1 and B1(P gt; 0.05). There was significant difference between groups A2 and B2(P lt; 0.05). Conclusion Closed-box knee prosthesis may play roles on reducing postoperative blood loss. The main influentialfactor for postoperative blood loss is operation techniques which includes reducing operation time and stanching thoroughlyduring operation.