Spider veins on thighs are small, damaged blood vessels located near the skin's surface. Also known as telangiectasia or thread veins, these clusters of tiny veins differ from varicose veins but can lead to similar symptoms. A small percentage of patients may experience symptoms such as red veins on my legs, tenderness, or swelling. USA Vein Clinics, the nation’s largest network of vein clinics, has a team of experienced vein doctors who specialize in treating painful spider veins on the legs using minimally invasive, FDA-approved treatments.