Evaluation of dose effect of BMP-7 for prevention of osteoarthritis progression in rabbit ACLT. (a) Representative macroscopic appearances of the distal portion of the femoral condyles at 12 weeks. Surface of the cartilage was stained with India ink to identify any fibrillation and erosion. Laterality is shown as lateral (L) and medial (M). Bar = 5 mm. (b) Representative histology of femoral condyles at 12 weeks. Distal femur was sectioned coronally and stained with safranin-O. The most degenerated area of each sample is included. Bar = 50 μm. (c) Quantitation of histological analysis using the OARSI cartilage osteoarthritis histopathology grading system. The scores are displayed as average ± standard deviation (three knees). *P < 0.05, by Mann-Whitney U test. ACTL, anterior cruciate ligament transection; BMP, bone morphogenetic protein; OARSI, Osteoarthritis Research Society International.