MMP13 and Osteochondroma: Reflecting the deranged growth plate-like organization within the osteochondromas, the expression patterns of Mmp13 and Col I were scattered (Fig 4I and 4J, arrowheads and arrows, respectively), and low Col I expression characterized the entire distal fibroblastic contour of the osteochondromas (Fig 4J) with stronger expression in flanking bone collar (Fig 4J, arrows).