Background: Pseudoaneurysms may appear in different sites of human body. In some percent of cases they result from bone exostoses and traumas. Case Report: A 16-year-old boy was admitted to our ward because of a gradually enlarging tumor in the lower 1/3 of his right thigh. It appeared after some hours of arduous marching in the mountains, accompanied with pain and mild ischaemia of the calf. Color duplex Doppler revealed a 12i6.5 cm liquid-filled space in the adductor canal, connected with the superficial femoral artery and the popliteal artery. Magnetic resonance angiography confirmed the diagnosis of a big pseudoaneurysm of the supragenual popliteal artery segment. The boy was operated on electively and a 1 mm wide defect in the anterior wall of the artery was found. It was closed by means of three interrupted sutures. The postoperative course was uneventful. During the surgery, the distal part of the femoral bone was found much wider than the rest of it with a very sharp posterior margin. This margin was supposed to be responsible for the repeated smaller injuries to the arterial wall. Conclusions: It is a rare case that repeated small traumas result in the rupture of the arterial wall. We also suggest that bone exostosis should be considered in all cases of pseudoaneurysms localized in the lower limbs.

Keywords: Popliteal Artery, pseudoaneurysm, bone, exostosis