Thanks for your advices, especially Ben.

Yes, most of the orthopedists I've seen diagnosed me with CP. When they press down on the area right above my kneecap I have big, sharp pain there. I think it tells you about you have some wearing not only on the cartilage also on the underlying bone. My MRI's also show a bit of bruising there but I think it shouldn't hurt if my kneecap was tracking normally.

Ben, I was riding on cold weathers at times but most of the time I was riding under warm weather. I don't think cold has been the number one reason that I got this. I had no idea about the cadence when I first started cycling and doing too much riding uphill with poor cadence. That should be the main reason. Anyway I will keep them warm if I ever ride again (I don't classify commuting as riding).

I have no problem touching my toes without bending my knees, I never had tight hamstrings problem.

I have been prescribed glucosamine many many times but I didn't use it for a long period. And the ones I used had chondroitin. I don't know why chondroitin should be excluded though.

Sometimes, for a week or two I am having pain free periods but as soon as I try to do a short ride I have my pain back again. I don't want to live a sedentary life but it looks like I have no choice.