Other things to help with problematic knees
Now, wouldn't it be great if we could all just go immediately from what's essentially dysfunctional use of the feet, legs, knees and hips, to wonderful alignment and a pain freeeee existence? Yes, it would. But unfortunately a lifetime's habitual (mis)use means that's at least very unlikely.
Chances are (and this had definitely been the case for me), you'll have tightness somewhere that needs releasing and weakness somewhere that needs addressing, in order to stand and walk and move around using the body in the most advantageous way.
Step one: spend as much time as you can with no shoes on. (I'm repeating myself, I know, but it's important.)
Here are some other things you can do to help your knees:
Practice standing in the way described above as often as you remember -- not just in a yoga class!
Hip stretches, hamstrings and calf stretches, high squat (chair or awkward pose), pressing down with one foot at at time on a tennis ball. (Click on the image below to see a picture of each of these.)