A bit of pretext: I've been having sporadic knee pains (left side) for the last 6 years now. I could never do any leg cardio like running or cycling. I went to four physicians/orthopedics, was x-rayed 2 times and went through 2 MRTs, with no results other then "you're still young and untrained, take it slow". The problem was no matter how slow I took it, my knee would hurt after, but seldom during, the exercise.
One day, some months ago I decided to screw it and go all out. Recklessly, I loaded up my barbell and started squatting. A funny thing happened, as my knees actually felt very healthy during the movement. What's more, my knees felt better the day after the squats too, and even more so as I progressed in weight lifted.
Six months later, I'm still having the occasional knee pain, but much less then before. Also, if I have this pain and do 3-5 bodyweight squats with good form, it goes away and stays away for several hours. It also works with back pain (from sleeping on a sofa, for example). Now there has to be some explanation, some physiological effect that I do not yet understand. If anyone could help me out and explain to me why squatting helps alleviate knee and back pain, I could probably use that effect more efficiently in the future.