- AKA Exostosis.
- Most common benign tumor or tumorlike lesion of bone.
- Composed of cortical and medullary bone with an overlying hyaline cartilage cap.
- It is the continuity of this lesion with the underlying native bone cortex and medullary canal that is pathognomonic of osteochondroma.
- These lesions result from the separation of a fragment of epiphyseal growth plate cartilage, which subsequently herniates through the periosteal bone cuff that normally surrounds the growth plate
- Lesions may be solitary or multiple, with the latter associated with the syndrome hereditary multiple exostoses (HME).
- Complications are commonly associated with these exophytic masses and include
- Cosmetic and osseous deformity
- Vascular compromise
- Overlying bursa formation
- Malignant transformation.
- Variants of osteochondroma:
- Subungual exostosis
- Dysplasia epiphysealis hemimelica
- Turret exostosis
- Traction exostosis
- Bizarre parosteal osteochondromatous proliferation
 Imaging Findings
 Plain film
- Sessile or pedunculated bone protuberance arising from the external bone surface and containing spongiosa and cortex that are continuous with those of the parent bone
- Typically, osteochondromas tend to point away from the nearby joint and toward the diaphysis. Widening of the metaphysis of tubular bones may be evident.
Patient #1: Rib osteochondroma
Patient #3: Subungual exostosis
 See Also
 External Links
- Mark D. Murphey, James J. Choi, Mark J. Kransdorf, Donald J. Flemming, and Frances H. Gannon. Imaging of Osteochondroma: Variants and Complications with Radiologic-Pathologic Correlation. RadioGraphics 2000 20: 1407-1434.