Effect of EPCR deficiency and rFVIIa treatment on joint bleeding and joint edema in hemophilia A mice following needle puncture of joint. Joint bleeding was initiated by needle puncture injury. Joint bleeding was evaluated by physical examination of knee joints and assigning an arbitrary score (A,C,E,G). Knee joint diameter, before the injury and alternate days for 2 weeks following the injury, was measured using electronic calipers. The diameter of the knee joint before the injury was subtracted from the diameter following the injury, and the differences in the diameter were plotted as the percentage (B,D,F,H). (A and B) WT (green), FVIII^−/− (red), EPCR⁺⁺FVIII^−/− (blue), and EPCR^−/−FVIII^−/− (magenta) mice following needle puncture of joints. (C-D) FVIII^−/− mice that were left untreated (red) or treated with a single dose (at 20 minutes following needle puncture, blue) or 3 doses (at 20 minutes, day 1 and day 3 following needle puncture, green) of rFVIIa (1 mg/kg). (E-F) EPCR⁺⁺FVIII^−/− mice that were left untreated (red) or treated with a single dose (blue) or 3 doses (green) of rFVIIa following needle puncture-induced joint bleeding. (G-H) EPCR^−/−FVIII^−/− mice that were left untreated (red) or treated with a single dose (blue) or 3 doses (green) of rFVIIa following needle puncture injury. Data are plotted as mean ± standard error of the mean (SEM) (n = 6). The data were analyzed by 2-way analysis of variance with Tukey’s multiple comparison test. Statistically significant differences identified in panels A and B were between FVIII^−/− and EPCR^−/−FVIII^−/− mice. In other panels, statistical significance was determined between untreated and rFVIIa-treated groups. *P < .05; **P < .01; ***P < .001; ****P < .0001.