The purpose of this study was to describe the magnetic resonance (MR)
appearance of a newly recognized complication of osteochondromas. Two
patients presented with pain and swelling over known osteochondromas.
Plain radiographic studies were unrevealing. MR examinations were obta
ined to characterize the exostoses further and evaluate areas of palpa
ble fullness. Increased signal was present in the muscles on T2-weight
ed images, which correlated with physical findings and was believed to
represent muscle injury due to the osteochondroma. Pain and fullness
may result from a number of osteochondroma-related complications, the
most worrisome of which is malignant degeneration. Muscular impingemen
t and injury should be considered in the differential diagnosis of pai
n and swelling in the region of an exostosis. MR imaging allows distin
ction of this entity, which may be radiographically occult and confuse
d clinically with fracture, bursitis, or malignant degeneration.