Evaluation of neoangiogenesis and cartilage degeneration in knee joints of FVIII^−/− , EPCR⁺⁺ FVIII^−/− , and EPCR^−/− FVIII^−/− mice 2 weeks after needle puncture–induced joint bleeding. Joint bleeding in FVIII^−/−, EPCR⁺⁺FVIII^−/−, and EPCR^−/−FVIII^−/− mice was induced by needle puncture of joints, and the mice were treated with a single dose or 3 doses of rFVIIa or left untreated as described in the Figure 1 legend. Fourteen days after injury, knee joints were excised, sectioned, and tissue sections were immunostained with the endothelial cell–specific marker CD31 (A) or Alcian blue for proteoglycans (C). As a control, knee joint tissue sections of uninjured mice were also stained. The original magnification of images shown in the top lane is ×4. The area identified in the square box was reimaged at higher magnification (×40) and shown in the bottom lane. Arrows point out newly formed blood vessels (A) and articular cartilage (C). (B) To quantify neoangiogenesis, the number of blood vessels positively stained with CD 31 was counted in multiple fields and averaged per field. (D) Cartilage degeneration was scored on a 0 to 2 scale (0, absence of cartilage degeneration; 1, partial loss of proteoglycan content and pannus formation; 2, complete cartilage degeneration/absence of proteoglycans, pannus formation, and femur remodeling). *P < .05; ***P < .001; ****P < .0001.