I have had my issues with my right knee this year and I finally believed that it was ok. Well, I went on vacatiion for two weeks and came back and did a fifty miler about 25 miles in my knee started hurting pretty bad (looking at my knee it is the top of the knee cap) Never had this issue before rode tonight and the pain is still there. Any thoughts on what might be the cause?

Old age.

I had this exact issue, except other knee.

I played around with a lot of things, couldn't get it to go away. Coughed up the money for a fitting session and it's gone for good.

seat to low or to far forward. check both