This a case of Trevor Disease, also known as dysplasia epiphysealis hemimelica (DEH). Imaging findings in this patient show the classic presentation of DEH. There is unilateral involvement of the left knee and ankle joints. The corticomedullary continuity of the bony excrescence at the level of the epiphyses is diagnostic of multiple osteochondromas arising from the femur and tibia.   

Recent evidence suggests that what were once thought to be osteochondromas are actually osteocartilaginous nodules that develop from abnormal epiphyseal cartilage proliferation and subsequent endochondral ossification. The lesions in DEH have also been shown to lack the genetic markers associated with osteochondromas. However, despite the current evidence regarding the pathological classification of these lesions, they are still reported as osteochondromas on radiological studies. 

Case contributed by Dr. N. Larocque.