I am 28yrs old. About a month ago we were having a party, and I was constantly moving(walking fast) to set things up. I had also started to push myself on the treadmill as well. I would get it up to about 3mph, which I know isnt that fast, but when you arent used to it, it is. Anyway, I had noticed that my one knee became sore. It is like a dull ache, just above the knee cap. I am not sure if there are muscles there, or if it is the knee itself. About 16 years ago, I sprained that knee and from time to time I would feel some soreness in it. BUt now it seems like anytime I exercise - even only 2.2miles per hour on the treadmill, it is that dull ache. There is a family history of arthritis, which also makes me nervous. Anyway, I was hoping someone would have some idea as to what this might be. Any advice would be appreciated. Thanks!!