Knee Position While Doing Kettlebell Cleans and Snatches

I'm somewhat confused about the proper position and/or movement for my knees when doing kettlebell Cleans and Snatches. I've been to YouTube.com and watched various Kettlebell clips but I just can't seem to find a definitive answer to proper knee positioning.

I've seen some people do these exercises where you "catch" the kettlebell with their knees bent (presumably to absorb shock), just like the Olympic variations. But then I've seen other clips where the person doing the workout "catches" the kettlebell with knees straight, maybe even locked.

Which of these is the proper form?

Answer