Stretching knee high boots?

You should be able to bring them to a shoe repair place and they'll be able to do it four you pretty inexpensively.

If you don't want to do that, here's an article with info on how to do it yourself:

http://www.ehow.com/how_2123064_stretch-boots.html

Stretch Knee High Boots

Let them sit out in the sun and stuff them with newspapers, go out every few hours and stuff more newspaper in them. If it is not sunny where you live then you can try blowing the hair dryer on them to make them hot. Heat will make them more elasticy and will also make them expand so you can stuff them with more newspaper