Comment by scotty79
Doing anything more than you should will trash something in your body. How much of something you should be doing? Pain is a good indicator. I you are below 40 you shouldn't feel it at all. If you are above, you should feel it a bit and observe it closely while reducing the load. If it gets weaker with time, you have appropriate load, if it doesn't or gets stronger, your load is still too high.
Some people just have bad knees, you know. But what you said for the most part is accurate in terms of exercise.