Healthy leg veins contain tiny one-way valves that open and close to assist the return of blood from the extremities toward the heart. The actual cause of varicose veins is usually inefficient, faulty vein valves. Varicose veins develop when the faulty valves in leg veins do not close properly, allowing blood to leak back with gravity and to pool in the leg veins. This causes veins to bulge and stretch. This increase in pressure or venous reflux leads to many symptoms of varicose veins such as aching, heaviness, tiredness, itchiness, numbness, fatigue, skin discoloration, swelling, restless legs, night cramps, hard knots in bulging varicose veins, and phlebitis (clots).
Heredity is a primary factor in over 80% of varicose vein cases.
Other exacerbating factors may include standing or sitting for prolonged period or time, injury, obesity, pregnancy, and hormone therapy.