Varicose veins are twisted, enlarged (dilated) veins near the surface of the skin. They are most common in the legs and ankles. They usually aren’t serious, but they can sometimes lead to other problems.
Varicose veins are caused by weakened valves and veins in your legs. Normally, one-way valves in your veins keep blood flowing from your legs up toward your heart. When these valves do not work as they should, blood collects in your legs, and pressure builds up. The veins become weak, large, and twisted.
Varicose veins are common and usually aren’t a sign of a serious problem. But in some cases, varicose veins can be a sign of a blockage in the deeper veins called deep vein thrombosis. If you have this problem, you may need treatment for it.