Has anyone tried Ido Portal's 30/30 Squat Challenge? This has been taking the internet by wildfire lately, and it's a very simple, effective move (or non-move, I should say) that will help with posture, knee strength, digestion, and overall health. Promoted by one of the foremost calisthenics/movement experts in the world, Ido Portal, the program, if you even want to call it that, consists of one simple premise - 30 minutes per day of being in the "squat" position (not the actual squat exercise) for 30 days straight.
Of course, you don't have to do all 30 minutes in a row. You can break them down whenever you have the chance, but just make sure that by the end of the day, the elapsed time accumulates to 30. I have only started for a couple of days, and I can already tell that my body feels more limber overall, and knees are definitely not as strained. Give it a shot, and let me know how it goes!