Evaluation of ectopic bone and osteophyte formation. 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. Knee joints were analyzed using a micro CT scanner at 12 weeks. (a) Representative three-dimensional CT images of BMP-7 treated and control knee. Lateral views show no obvious ectopic bone formation in BMP-7 injected side and control side. (b) Representative reconstructed CT images of distal femoral osteophyte. Osteophytes were colored with yellow by image processing. Laterality is shown as lateral (L) and medial (M). (c) Quantitation of osteophyte volume. The values are displayed as average ± standard deviation (n = 5). BMP, bone morphogenetic protein; CT, computed tomography; PBS, phosphate-buffered saline.