Osteochondroma

A noncancerous bone tumour, which is formed from a stalk of bone capped with cartilage, and appears as a hard round swelling near a joint. An osteochondroma develops in late childhood and early adolescence, usually from the side of a long bone near the knee or shoulder. The tumour causes problems only if it interferes with movement of tendons or the surrounding joint, in which case it may be removed surgically. Large osteochondromas can interfere with skeletal growth, causing deformity.