Varicose veins develop due to incompetence of the one-way valves in the veins, allowing retrograde blood flow and pooling in the superficial veins. This causes the superficial veins to dilate and become tortuous. Risk factors include family history, older age, pregnancy, and history of deep vein thrombosis. Diagnosis is based on history and physical exam, with duplex ultrasonography used to detect reflux and evaluate venous anatomy. Treatment options include compression therapy, sclerotherapy, thermal ablation, and surgery to ligate or strip the refluxing vein.