I used to squat with up to 400 Lbs. in high school. But I injured my knee in the bathroom after over a decade of inactivity (that began with an ankle injury). Then I injured the other knee while limping around favoring the injured knee. Anyhow after thinking my knee joints were both shot for good and not having the money or bravery to have a doctor check them out, a guy turned me onto Glucosamine Sulphate and they stopped popping all the time and felt better. I quit the glucosamine after my knees got better, and they have since gotten worse, but not as bad as they were. So now I'm back to taking glucosamine and I'll be squating tonight with probably around 135 - 155 Lbs. to try to rehabilitate my knees and exercise myself. I'm trying to work gradually back into things and not incur an injury by lifting too much too soon. I don't want to become the guy who only exercises his upper body.