One of the things that I always used to freak out about when teaching was seeing someone's knee go past their heel during Warrior 2, because I was initially taught that it could be dangerous for the knee. And I've heard that sentiment repeated in other yoga classes by countless other yoga teachers. But is it really unsafe? If so, then why do we allow the knee to travel forward of the heel in Malasana? When preparing to kick up into handstand? For that matter, what about when we climb up or down stairs, or squat in front of the refrigerator? What's the deal with the knee and the heel?