Samatvamasana and Turbo Practice

This Sunday in my Power yoga class I used the poses from the latest Yoga Journal issue. Samatvamasana (or was it Samatvasana?) - squat on the toes, + twist, + 1 leg in lotus, + one extended leg. I both liked and disliked these poses. On the positve side - nice balance (different from standing or arm balaces); plus these poses give an amazing workout to the ankles and toes. But they were really hard on the knees, some of my students could not do them at all. In my teacher training program I heard many, many times that the movement of the knee over the toes in the knee bend is really bad for the ligaments of the knee. So what about the squat? Doesn't it put the knees into exatly the wrong positon we were warned against? Or keeping the heel up somehow changes the things? Do not understand, really. I will probably not use them in the class anymore untill I get a better "feel" of these poses.
This morning I had a "turbo practice". Once in a while we have a very early experiment at work, so I have to be there at 7 am. Actually, my work normally starts at 7, but most days it is relaxed, and I can arrive at 7:30 and have no problems.In the "early experiment" days, I start my practice around 5:30-5:45, and finish it by 6:30. It is not quite possible for me to finish the full primary in 45 min, so I hold poses for 4 breaths, and try not to spend more than half a breath while transitioning. Did not have time to work on my getteing up from the wheel though. Nevertheless, the turbo practice is much, much better than no practice at all, I feel just as great as after a "normal" practice.