Knee Issues

Started having some knee issues right after my first 10 miler last week. I'm assuming it's due to the fact that I ran so long but I'm also wondering if it might have anything to do with the fact that my 2120s have about 300 miles on them. I keep telling myself that I *just* got these shoes in February. There's no need to buy new ones yet. Then I remember, it's June/July. I'm pushing 5 months in these shoes. This month alone I ran over 100 miles so I think it's just time for a new pr. I recently got those Kayanos but I'm not lovin' 'em. I ran in them yesterday, hoping they would help but I just didn't feel comfortable in them. Meh, we'll see. Not sure what to do but it would seem I need to make a decision today. No running today, day off. But I should figure out what I'm going to do before my run tomorrow.