I'm in my mid 40's, and I've gone basically my whole life with "bad knees". Nothing bad enough for surgery, but I stopped skiing, stopped playing volleyball, and tried to avoid events where I'd be standing around all day, because I'd end up with aching knees, or the fear of injury, or...whatever.

After squatting for a few months, I realized my knees don't hurt anymore. I didn't have bad knees; I was just weak. For 30 years. Gah. I could have done this in college! My roommate even offered to show me how!

'course, now I'm a little bit sore everywhere basically all the time, but I'll still call it an improvement