Hello, I have had some experience with knee pain and the such on and off the bike. It turns out that my patella (kneecap) wasn't tracking the right way. After going to my doctor I was refered to the Orthopedic doctor with "water on the join" bassically my knee was slightly swollen. After going to the Ortho I found out that my patella wasn't tracking right and was given a Physical Therapy sched. If the pain keeps on happening I would go to the doc and see whats up. According to my doc (not sure if this true or not) he said that riding (atleast in my case) may have caused the patella tracking issue. As the others have suggested it may be a sizing problem. Just thought I would tell you because it may help you out in the long run. Hope this helps and hope that you are not in too much discomfort.