Multiple hereditary exostoses (MHE) is an autosomal dominant disorder manifested by multiple osteochondromas, which are benign tumors projecting from the surface of bones. The incidence of MHE is 1 in 50,000 individuals.  The exostoses are either sessile or pedunculated, and are located at or close to the metaphyses of the bones involved. Although osteochondromas are benign lesions, they sometimes cause skeletal deformities which may in turn cause clinical symptoms. Short stature is present in 40% of patients.  The painless masses can become painful when they impinge upon tendons, muscles, or nerves. Other symptoms include bursitis, fractures, premature osteoarthrosis, weakness or numbness due to impingement of an adjacent nerve, blood vessel aneurysms, and loss of range of motion.

The most serious complication of MHE is the potential for an exostosis to undergo malignant transformation into chondrosarcoma. In skeletally mature patients, the cartilaginous cap should be measured.  If the cap is >1 cm thick, there is an increased risk for malignancy.  T2-weighted MRI images are the most useful in evaluating the cartilaginous cap.