I have never experienced any problems while on the bike whether mashing or spinning. Not even a twinge. Lately, I've noticed that after riding, just walking, for the next 15 to 20 minutes is a problem. No steady pain but sometimes it's as if my knees just start to buckle and I get a twinge of shooting pain. Soon, it just goes away.
Basics...I'm not riding huge distances, just 15 to 30 miles or so. My speed is from 13 to 15 average with occasional peaks at 20 mph or so. This occurs whether I'm riding my road or mountain bike. I'm very confident that both bikes properly fit me. I'm in my mid 50's and just back to biking for a year or so and also a shrinking clydesdale. I'm not in great shape but I'm not totally out of shape.