I have spider veins on both legs and have severe knee and leg pain, also the veins swell up and causes it to be hard to sit, stand, and walk.

This is more than: "spider veins." you sound as if you also have true varicosities, and may have stasis dermatitis, edema, and/or vascular insufficiency. You should see your family doctor, who may refer you to a vascular surgeon who specializes in all of these issues. You may also have orthopedic issues with your bones and joints, in addition to your venous problems. Get this checked out!

Varicose veins: Your are having symptomatic incompetent valves of your leg veins causing blood to pool and distend the veins particularly with prolonged standing. Medical grade compression stockings will help to ease the discomfort. Treatment is aimed at identifying the faulty veins and removing or closing them. This usually requires ultrasound imaging performed by a specialist.

More than spiders: You have more than just spider veins - you have symptomatic varicose veins. These can be treated, so you can be more comfortable. See a local vein specialist.

More than spiders: It sounds pretty clear that you have more going on than just spider veins, as the other doctors have said. I completely agree, if you are having that much trouble with your varicose veins, it is time to see a vein specialist and do something about them. Treating you varicose veins will likely help your spider veins in the process.

Other reasons.: In addition to your spider veins, you sound as if you may also have varicose veins. Your symptoms, however, are not typical of just vein problems. You should start with a full venous evaluation by a vein specialist including a venous reflux ultrasound. Depending on this, you may also need to have other causes of your symptoms evaluated such as orthopedic and neurologic.