My guess is your knees are still sore because you were lifting your chest before. It should get better. Yes your torso should be ridgid.
Your knees are not going to magically get better in a few days. It may take a week or a month. I had a similar problem in my hips when my squat stance was too wide. My pain/soreness went away in two weeks after taking some ibuprofen, deloading, and focusing on squatting with good form.
Your squats are getting better. Fix the remaining bugs and be patient.
Last edited by TurtleBack; 03-17-2017 at 11:13 AM.
One more try with added weight.
You can see me getting a big breath in my belly and making everything tight.. My back is not rounding like the last one also.
But felt tightness in my lowerback after the set. Is that normal. Should i continue adding weight.