Growth plates are areas of developing cartilage tissue near the ends of long bones in children. Bone growth occurs from the growth plate, and when a child is fully grown, the growth plates harden into solid bone.

An osteochondroma is an outgrowth of the growth plate and is made up of both bone and cartilage. As a child grows, an osteochondroma may grow larger, as well. Once a child has reached skeletal maturity, the osteochondroma typically stops growing, too.

In most cases of osteochondroma, no treatment is required other than regular monitoring of the tumor to identify any changes or complications.Osteochondromas can develop as a single tumor (osteocartilaginous exostosis) or as many tumors (multiple osteochondromatosis). Because symptoms and treatment options may vary depending on which form a patient has, this article discusses them separately.