An abnormal nodule or small mass of overgrowth of bone, usually occurring bilaterally and symmetrically, in juxtaepiphysial regions, especially in long bones of the lower extremities; lesions are not actually neoplasms, but represent anomalous developments in which there are outpouchings of the cortex (in contrast to a growth superimposed on the cortex), and are more properly termed exostoses. [osteoma + G. eidos, appearance, form]