Muscle pump failure occurs in any condition where the calf muscles are very weak. If this persists it also causes valve failure. By far the commonest reason for venous insufficiency and varicose veins is valve failure which can result from inherited valve defects (most common); hormones (eg in pregnancy); trauma, previous thrombosis or weak calf muscles. Once one valve is damaged allowing reflux through it this causes the vein below to stretch. This causes the next valve down to be pulled apart and also fail ,leading to a domino type effect with more and more valves failing and eventually a varicose vein becomes prominent. So you can see the most important factor is your genes; did your mother have varicose veins? When the valves fail blood flows the wrong way through the veins away from the heart. This is called reflux. The detection, localisation and treatment of reflux is crucial to the effective management of all venous insufficiency problems including varicose veins, reticular veins, spider veins and ulceration.