Purple blood vessels on the soles of the feet may be caused by varicose veins, venous thrombosis of the lower extremities, or knocks. 1. Varicose veins: due to poor venous return, there is a dilation of tiny capillaries, and the blood vessels on the soles of the feet will be purple due to lack of oxygen. 2. Lower extremity venous thrombosis: when the lower extremity venous thrombosis, the blood return is blocked, then the plantar vessels will appear purple, often accompanied by pain and other symptoms. 3. Bumping: Due to bumping into the soles of the feet, there is rupture of small blood vessels, bruising will also have purple blood vessels can be recovered on their own. 4. Other reasons: If there is serious heart function damage or lung problems, when the oxygen carrying capacity of blood vessels is weakened, there will be cyanosis of lips and mouth in addition to purple blood vessels on the soles of the feet. So if you have purple plantar vessels must be taken seriously, go to the hospital as soon as possible.