They generally occur at the end of the growth plates of long bones, often at joints. They most commonly form at the shoulder or the knee but have been known to occur in the long bones of the forearm (i.e. the radius and ulna).
Osteochondroma, one of the most common benign bone tumors, takes the form of a cartilage-capped bony spur or outgrowth on the surface of the bone. It is sometimes referred to as osteocartilaginous exostosis. When an exophytic bone lesion contains a cartilaginous cap greater than one centimeter in height, or if there is associated pain, there is thought to be a higher risk for the lesion representing a chondrosarcoma.
On most occasions the tumors grow outward from the legs or arms. However, very few cases have been reported with the bone spur growing inward, sometimes requiring surgery. Osteochondromatosis is a condition involving a proliferation of osteochondromas.
Surgical extraction of osteochondromas is sometimes beneficial. Shown is an osteochondroma surgically extracted from a ten-year-old patient. The bone is the cylindrical stalk at the bottom, about 1/2 inch long, the two diagonal growths are cartilage. This morphology is typical of a tibial bone spur.
Osteochondromas are most often, upon diagnosis, simply monitored through periodic x-rays. Those tumors that grow large enough to irritate surrounding muscles, tendons, or tissues are usually removed by surgery.