Have a vein above knee hurts bad and is blue why would this be?

Inflammation: Hi there If it is red and warm it could be thrombophlebitis, which just means the vein has a small clot in it and got inflammed. Nothing dangerous. Apply heat every 30-60 minutes for 10 minutes or so, take Motrin as directed and it will resolve If it's not red and warm but bulging it is likely a varicose vein which is easily treated by a physician who does vein work.

Varicose.: It could be a varicose vein, in other words, that part of vein may not be functioning normally. See a vascular physician for evaluation.