Varicose veins develop when the tiny one-way valves inside your leg veins stop working properly, allowing blood to flow backward and pool instead of traveling back up toward your heart. About 23% of U.S. adults have them, and they’re roughly twice as common in women as in men. The reasons you specifically developed them come down to a mix of genetics, daily habits, and physical changes your body has gone through over time.
What’s Happening Inside the Vein
Your leg veins contain small flap-like valves that open to let blood flow upward and snap shut to prevent it from sliding back down. When these valves weaken or stop closing fully, gravity pulls blood backward into the vein below. That backflow, called reflux, creates persistent pressure on the vein wall.
Over time, the extra pressure stretches the vein. As the vein widens, the valve cusps that once met in the middle get pulled apart even further, making the problem worse. The vein keeps dilating, eventually bulging close enough to the skin’s surface that you can see and feel it. This is why varicose veins look ropy, lumpy, or three-dimensional, unlike spider veins, which are flat, wispy clusters less than a millimeter wide that you usually can’t feel with your fingertip.
Genetics Play a Major Role
If your parents have varicose veins, your odds of developing them are high. One study of 134 families found that when both parents had the condition, their children faced a 90% chance of developing varicose veins themselves. The inherited component likely involves the structure of your vein walls and valves. Some people are born with valves that are slightly less resilient, or vein walls that stretch more easily under pressure. If varicose veins seem to run in your family, that’s probably the single biggest reason you have them.
Standing and Sitting for Long Stretches
Your calf muscles act as a pump for your veins. Every time you walk or flex your calves, the muscles squeeze the veins and push blood upward. When you stand still for hours, gravity forces blood to stay in your lower legs with no muscular pump to counteract it. The sustained pressure gradually wears on vein walls and valves.
Sitting for long periods creates a different but related problem. When your legs are bent at the knees, blood flow through the lower extremities slows down and pools. Without regular movement, that pooling puts extra pressure on the veins and weakens their function over time. Jobs that keep you in one position, whether on your feet at a retail counter or seated at a desk, increase your risk significantly if you aren’t taking movement breaks.
How Body Weight Affects Your Veins
Carrying extra weight, especially around the abdomen, increases the pressure inside your abdominal cavity. That elevated pressure gets transmitted downward into the veins of your legs, forcing them to work harder to push blood back up. Research shows this increased lower-extremity pressure damages the tiny valves in the skin’s smaller veins first, then contributes to reflux in larger veins over time. The combination of higher pressure and lower blood flow velocity triggers inflammatory changes in the vein walls that accelerate the process.
Pregnancy, Hormones, and Age
Pregnancy is one of the most common triggers for varicose veins. The growing uterus compresses the large veins in the pelvis, restricting blood return from the legs. Blood volume increases substantially during pregnancy, adding even more load to the venous system. Hormonal shifts also soften vein walls to accommodate the extra blood flow needed for the baby, which makes the veins more prone to stretching.
Hormones play a role outside of pregnancy too. Estrogen and progesterone relax smooth muscle in vein walls, which is one reason varicose veins are more common in women. Between the ages of 40 and 80, an estimated 22 million women and 11 million men in the U.S. are affected. Age itself is a factor because vein walls and valves lose elasticity with every passing decade, the same way skin does.
What Happens If They Get Worse
Varicose veins aren’t just cosmetic for everyone. Venous disease is classified on a scale from stage 0 to stage 6. Visible spider veins fall at stage 1, and varicose veins wider than 3 millimeters sit at stage 2. Many people stay at these stages with no significant symptoms beyond aching or heaviness at the end of the day.
But when reflux persists untreated, some people progress. Stage 3 brings noticeable swelling in the lower legs, particularly around the ankles. At stage 4, the skin around the ankles starts to change color or texture, often turning brown or becoming leathery. Stages 5 and 6 involve venous ulcers, which are open wounds near the ankle that heal slowly or keep reopening. This progression can take years or decades, and not everyone moves through every stage, but persistent symptoms like skin discoloration or swelling that doesn’t resolve overnight signal that the condition is advancing.
How Varicose Veins Are Diagnosed
A doctor can often identify varicose veins by looking at your legs while you’re standing. To understand the severity and plan treatment, they’ll typically order a duplex ultrasound. This painless test uses sound waves to watch blood flow through your veins in real time. The technician squeezes your calf and then releases it, measuring how long blood flows backward after the squeeze. In superficial veins, any backflow lasting longer than half a second is considered abnormal. In the deeper veins behind the knee or near the groin, the threshold is one second. These measurements tell your doctor exactly which valves have failed and how extensive the reflux is.
Reducing Pressure on Your Veins
You can’t change your genetics, but you can reduce the daily pressure load on your veins. Moving your legs regularly throughout the day is the simplest intervention. If you sit at a desk, flexing your ankles or taking a short walk every 30 to 60 minutes keeps the calf pump active. If you stand for work, shifting your weight and bending your knees periodically helps.
Compression stockings apply graduated pressure that’s tightest at the ankle and loosens as it moves up the leg, helping push blood upward. They don’t reverse existing varicose veins, but they reduce symptoms like aching, swelling, and heaviness. Elevating your legs above heart level when resting also lets gravity assist blood return instead of fighting it. Maintaining a healthy weight lowers the intra-abdominal pressure that contributes to reflux, and regular exercise, particularly walking, cycling, or swimming, strengthens the calf muscles that serve as your veins’ natural pump.
When varicose veins cause persistent pain, skin changes, or complications, several minimally invasive procedures can close off or remove the damaged vein. The body reroutes blood through healthier veins nearby. Most of these treatments are done in an office setting with local anesthesia, and recovery typically involves returning to normal activity within a few days.