When veins have to work extra hard to get blood back to your heart, they bulge and look twisted, blue, or dark purple. They can make your legs feel heavy, burn, throb, or cramp. You’re more likely to have them as you age, or if you’re overweight, pregnant, or stand or sit for long stretches. Losing weight, exercising, or wearing compression stockings may help. If they don’t, talk with your doctor about other treatment options.