Exostosis

An exostosis (plural: exostoses) is the formation of new bone on the surface of a bone. Exostoses can cause chronic pain ranging from mild to debilitatingly severe, depending on the shape, size, and location of the lesion.

When used in the phrases "Cartilaginous exostosis" or "Osteocartilaginous exostosis", it is considered synonymous with Osteochondroma. Some sources consider the terms to mean the same thing even without qualifiers, but this interpretation is not universal.