Osteochondroma is the most common type of benign bone tumour, and is most often found in the knee region. The lesion is usually clinically silent although it may cause different complications such as fractures of the tumour, bone deformities, neurological disorders, malignant transformation and in rare cases vascular disorders. Vascular disorders include stenosis, occlusions, thrombosis, arteriovenous fistula and in rare cases pseudoaneurysm formation. A delay in diagnosis especially of pseudoaneurysm formation may result in life-threatening situations, extensive operations and lengthy hospital stays. We report the case of a 22-year-old woman with an osteochondroma of the distal femur which caused pseudoaneurysm of the popliteal artery.