Complications of multiple exostoses occur rarely and articles about it can be found occasionally. We found reasonable to report our case because of its rarity. A female patient of 17 was under treatment in the Orthopaedic Clinic with multiple exostoses. Before her admission to the Clinic, a suddenly, painful swelling in the distal-third of the left femur occurred, and then a well detailed examination has done (bone radiograph, angiogramm, MR). The examinations arised the presence of pseudoaneurysm as a background of the swelling of the soft tissue, as well as the possibility of juvenile bone tumor at the same time. During the operation we detected a sharp exostosis on the distal medial condyle of the femur, which occurred a lesion on the popliteal artery. It was the base of forming the pseudoaneurysm. As a conclusion we would like to underline that during the attend of such cases, the presence of vascular surgical team is necessary.