A venous ulcer (also called a venous stasis ulcer or varicose ulcer) is a chronic, non-healing sore that usually appears near the ankle when veins malfunction and blood pools in the lower leg. Venous ulcer causes include chronic venous insufficiency, where damaged vein valves fail to send blood efficiently back to the heart. At a vein clinic like USA Vein Clinics in Queens, vein specialists can assess vein health, often using ultrasound and offer minimally invasive treatments to improve circulation.