Acute popliteal pseudoaneurysm rupture secondary to distal femoral osteochondroma in a patient with hereditary multiple exostoses.

A 21-year-old man with known hereditary multiple exostoses presented with a 24-hour history of atraumatic bruising and swelling of the posterior thigh. A leaking popliteal pseudoaneurysm was diagnosed on ultrasonography and an emergency saphenous vein bypass graft procedure performed. The patient required a post-operative blood transfusion but otherwise made a full recovery. Vascular complications from osteochondromas are rare and include vessel displacement, stenosis, occlusion, arteriovenous fistulas and pseudoaneurysm formation. Pseudoaneurysms usually present as an enlarging mass behind the knee. Acute rupture of an occult popliteal pseudoaneurysm caused by a distal femoral exostosis has not been reported previously.