Knives pack a triple no-no whammy in the dishwasher. First, the edges can nick the protective coating on racks and baskets causing rust to form. Secondly, those sharp edges are dangerous when unloading the dishwasher especially when kids are helping.
Finally, the harsh dishwasher detergent can dull edges and cause wooden handles to loosen and split. It's best to hand wash all types of kitchen knives.
Comment: I'm afraid I'm guilty of this. I had no idea it would damage my knives. Guess that's why I have to sharpen them so often.