No differences in initial joint bleeding in FVIII^−/− mice administered with MPC1609 and MAPC1591 following the needle puncture of the joint. FVIII^−/− mice were administered with control IgG, MPC1609, or MAPC1591 (1 mg/kg) ip. Twenty-four hours later, the right knee joint capsule of the anesthetized mouse was punctured with a 30 × 0.5-g needle below the patella to induce bleeding into the joint. The left knee joint of the same animal served as uninjured control (UN). Five hours following the injury, the mice were euthanized, and the skin was removed over the knee joints. The knee joints were photographed, and joint tissues were processed to extract hemoglobin. Blood samples were collected from the submandibular vein puncture before euthanasia to measure hematocrit and hemoglobin content. (A) Representative photographs of uninjured and injured knees; (B) hemoglobin content extracted from joint tissues of uninjured and injured knees; (C) hematocrit; (D) hemoglobin levels in peripheral blood samples. ns, not statistically significant difference. **P < .01; ***P < .001; ****P < .0001 (n = 4 mice per group).