Here's a link to a good publication on pruning roses.

I wait until early spring when I can tell which canes, if any, are dead. These I cut back to living tissue or to the base, depending on the amount of dead cane.

You should not need to prune Knockouts or their relatives at all. In fact, the plants will have a nicer overall shape if you leave them alone. My Blushing KOs are leafy and have flowers to the ground every year and I don't cut anything except the reversions (and not even all of those).

I am at the beach and we pruned last weekend like our local rose society suggested. I would wait at least another week for you. I know it is supposed to get down to the 30's a couple of nights this week down here. The last frost date for your area is a good guide line.