Causes

Weak or damaged valves can lead to varicose veins. Arteries carry blood from your heart to the rest of your tissues, and veins return blood from the rest of your body to your heart, so the blood can be recirculated. To return blood to your heart, the veins in your legs must work against gravity.

Muscle contractions in your lower legs act as pumps, and elastic vein walls help blood return to your heart. Tiny valves in your veins open as blood flows toward your heart then close to stop blood from flowing backward. If these valves are weak or damaged, blood can flow backward and pool in the vein, causing the veins to stretch or twist.