The lateral plantar vein is not usually examined during the search for lower extremity deep vein thrombosis. Fortunately the circumscribed symptoms drew my attention to the sole of the foot. 

Plantar vein thrombosis is a rare condition, with less than 100 cases published in the literature. The lateral plantar vein is affected most commonly (96% of cases). Plantar pain and circumscribed oedema are its major clinical signs. The most important potential complication is further progression into the deep venous system and development of pulmonary thromboembolism ¹.