Why do I get pain down my legs when I get cramps?

Muscle spasms. I am assuming that the cramps you are describing are leg cramps. The large muscles in the legs experience pain when the muscles contract and don't let go, causing pain that can shoot down your legs. This can be a sign of poor circulation, abnormal salts (especially potassium, magnesium, or calcium), and should be evaluated by your primary physician. Good luck!