How can clogged blood vessels hurt my legs and feet?

Peripheral vascular (puh-RIF-uh-rul VAS-kyoo-ler) disease can happen when the openings in your blood vessels become narrow and not enough blood gets to your legs and feet. You may feel pain in your buttocks, the back of your legs, or your thighs when you stand, walk, or exercise.

source: http://diabetes.niddk.nih.gov/dm/pubs/complications_heart/index.htm