Immunohistochemical analysis for BMP-7 in cartilage. After anterior cruciate ligament transection in both knees, 500 ng BMP-7 in 200 μl PBS was injected weekly into the right knee and the same amount of PBS was injected into the left knee. The remaining cartilage in medial femoral condyles was evaluated at 12 weeks (7 days after the last injection). Higher magnifications are demonstrated in the right column. Bars = 10 μm. BMP, bone morphogenetic protein; PBS, phosphate-buffered saline.