This is a varicose vein. Varicose veins run in families and are more common in women. They often ache, sometimes itch, and usually cause swelling and pain in the feet and ankles. After the blood has delivered oxygen throughout the body, veins carry it back toward the heart.
Veins have one-way valves to keep gravity from pulling the blood downward.
In varicose veins, the valves leak. Accumulated blood at these leak sites stretches the vein, and pools of it cause lumps and kinks. The veins affected are just under the skin, so you can clearly see the enlarged and twisted portions. Sometimes, varicose veins first occur during pregnancy because of hormonal changes and increased pressure in the veins caused by the expanding uterus. Obesity, menopause, aging, and repeated abdominal strain, as with heavy lifting, may contribute.