Varicose veins are enlarged, rope-like veins that occur in the legs of both men and women. Often dark blue in color, they appear near or even raised above the surface of the skin.
Varicose veins don't develop suddenly. In fact, they usually take years to develop. While they're often inherited, anyone can get them. And they're common for people who have had certain types of leg injuries or deep-vein blood clots.
Another factor for developing varicose veins is doing work that requires standing or sitting for long periods of time. This deprives the veins in your legs of the regular blood flow that occurs when your leg muscles flex during walking and other activities.
As you go about your day, blood flows from your heart to the rest of your body through arteries. It then returns to the heart through veins. It first collects in small superficial veins, then flows into larger veins that have one-way valves to keep the blood from flowing backward.
In healthy veins, these valves make sure the blood is directed upward and inward toward the heart and lungs. But when one or more of these valves don't work properly, some of the blood leaks and flows back down the leg. This causes the vein to overfill with blood, making the branches of those small superficial veins bulge under the skin.
Varicose veins also occur because of incompetent perforators. Deep veins communicate with superficial veins via perforators. Normally the blood flows from superficial veins to deep veins. If the flow is reversed the superficial veins can become varicose.