Make sure you're stretching your quads. A lot of people complaining of knee pain are getting it due to very tight quads, which will pull on the tendons around the knee and cause pain/inflammation. Personally, the one I like the best is where you sit on your heels while kneeling. If you don't get enough of a stretch just sitting there, then lean backwards until you feel it. I'll do this many times a day for 20 sec to a minute each, and rarely have knee pain.