Knee pain

When I first was trying to figure out the glidewalking technique from the book in the weeks before I took the class, my left knee started hurting and I have never had knee pain in my life.  I slowed down to where I was walking in slow motion to see if I could figure out what was going on. I found that right before I put my left leg down, the muscle at the top of my knee on the front of my leg would grip just before my foot touched the ground.  My right leg wasn't doing this.  I think I was trying to soften the footfall on the left side by pulling back with my front leg muscles before landing. I was able to make it stop but I couldn't walk any faster and I gave it up completely so I could start fresh at the class.  At the class, I figured out that I wasn't focusing enough on correctly landing the front leg with a bent knee.  I feel like I was still trying to be tall when walking by making my legs tall even though with a bent front knee and the other leg straight out behind me, I had to be a little lower to the ground than when standing.  So I think of it more now as being tall with the spine and letting the hip sink into the walking.  Also, it seems for me, that getting the front leg completely relaxed means that the whole leg feels like it acts a little bit like a spring after landing. I let my weight sink into it after landing so that the whole leg absorbs some of the weight, kind of like doing a miniature lunge and then activate the muscles to straighten and pull the leg backwards. The other part of it for me that I noticed is that even though it is very quiet and gliding, my upper body isn't just floating along. It kind of goes up and down slightly like a very a smooth wave.  This is because the pulling leg is straight up and down when the swinging leg is crossing making me taller and then when the front leg is landing and the heel is back on the ground that makes me lower.  I don't know if you are doing what I was doing but I would say try to focus on relaxing that swinging leg not just at the knee but also at the groin so that the whole leg can be a little springy and not stiff.  Hope this helps.

Natecase says it well, I think. Make sure you are truly relaxing the front leg, both at the knee and at the hip. When you first find this way of walking as a series of mini-lunges, you may rise up and down some, but you want to evolve your form to where there is relatively little up and down.

I wouldn't say the point is to not use the quads. To not plop down on the legs each time seems like a worthier point, but really the point of glidewalking is to walk in the healthiest possible manner, the way you were designed to walk. This gives in a multitude of benefits. You get from one place to another, you exercise various muscles especially the glutes (which in turn has a myriad benefits), you spare all your weight-bearing joints, you stretch your psoas and calves, etc. etc. Glad to hear about your progress and exploration!