by chh » Wed Mar 05, 2014 12:50 pm
Hello! I think knees not going over the toes is part of this. As I understand, as you condition your knees more, going beyond that angle is less dangerous, but it's still a potentially stressful position for the knees.
But I think the main 'knees line up with the toes' point is that the direction that your knee joint is pointing in (in front of you, to the side, etc.) should be lined right up with the direction your toes are pointing in.
For example, if you're in a front stance with your front foot wherever it normally points, your knee is likely pointing the same way. If you shift your weight back and turn your waist, it may be the case that your knee twists with that motion despite your foot staying still. This can be really stressful on the knee, and I think it's what that recommendation is about. The more flexibility you have in the kua, the easier it is to keep the knee aligned with the toe in that situation.