It could be due to lack of cartilage around the bone ie arthritis Bone on bone and pounding on the pavement might be causing the pain. Try running barefoot. It is all the craze at the moment. If you are using cushioned soles like say Nike air you are probably hitting the road with your heel first What the running barefoot does is that you start running naturally on the ball of your foot The foot, the knee in fact the whole leg becomes a spring I used to only be able jog half an hour before the knees started hurting and I had to stop and start walking I can now jog for an hour and I have almost zero pain. My feet are too delicate for that so I am doing the next best thing using a barefoot runner There are many kinds. here are mine
you can even get some with toes.
the interesting thing about this is that it goes against what you'd normally think. You'd think cushioning in the shoe would be the solution but it isn't. If anything it is the cause of the problem.
