My family knows a man who had this issue. He did go to the Doctor though he never said if he solved it or whatnot. He does drive a bus and encountered this issue only when driving. I think he said not with my car cause the pedal is softer but the bus has a more engrossing pedal.
I think the main knee pain is not so much the knee itself. I think it's the cartilage that acts like a lubricant to move the knees fairly.
So in essence your issue is not the bone nor the knee itself but the pinching of the knees lacking in a reduction of the matter that allows smooth, easy movement.
Try this does your knee hurt at all times or when doing other things. Sounds like only when your driving. So if this is the case then I don't think it's a ligament or bone issue but the matter providing a surface to move the knees.
Do you roughly move your knees? Do you exercise a lot? Do you squat with/out weights?
I think it might just be the matter in between the knee and not the knee itself. If this only happens while driving then I think like I said the matter might seem normal in other times but with the car your pinching this matter thus your knees hurt.