I don't have pain.
I once visited a doctor before, she checked my bones and muscles, and found out that I have 'very flat feet'. She said I need to take care because with this kind of feet, the body will automatically put more pressure on the 膝蓋. Now, when I am young and I am quite thin (lucky), I don't have much pressure now. However, if I get older and gain more weight as age increases or carry too much baby, the 膝蓋 will have more and more pressure which hurt. Therefore, I need to be careful and do some prevention. For example, the doctor made me a special shoes pad that I can add into the shoes to raise the 'curve' part of my feet.
Of course, I am not sure in your case. I think it's better for you to get some professional advice from doctor because there can be many different reasons that leads pains on 膝蓋.