Osteochondroma is a common benign bone tumor that sometimes causes vascular complications when the lesion is situated near the knee. Venous complications are seen less frequently. We report two cases of solitary osteochondroma that arose in the distal femur. The patients were an 11-year-old boy and a 16-year-old boy, both of whom were suffering from bone protuberance and lower leg swelling due to congestion. In both patients, magnetic resonance imaging (MRI) revealed dilated popliteal veins at a site distal from the tumors or superficial veins. MR angiography (MRA) showed compressed popliteal arteries, and Doppler ultrasonography revealed weaker blood flow in the dorsalis pedis arteries in the lower leg with the tumor than in the other lower leg. The former patient complained of pain due to swelling in the lower leg, and for this reason the patient underwent resection of the tumor. After resection, both the swelling and the pain were decreased, and Doppler ultrasonography also revealed normal blood flow in the artery. The latter patient had swelling, but no pain, in the lower leg, and accordingly this patient has been followed carefully without resection, since there is always the possibility of irreversible vascular damage caused by osteochondroma, such as arterial or venous occlusion. We present two patients with osteochondroma, both of whom suffered from swelling of the lower leg due to venous compression by the tumor. In both cases, MRI and MRA were useful to show the presence of vascular compression. Doppler ultrasonography could also reveal the blood flow disturbance objectively, even in current osteochondroma cases in which there were no arterial symptoms.