I fell on my left knee hard at work and it hit a metal floor. If I touch it in a certain spot with only a pound or two of pressure it is extremely painful, and this is 3 years after the original accident. I can walk all day or ride a bike for miles, it only hurts when something taps it or I put my weight on it, but very annoying. I am 41, 5 8. There is nothing visually wrong, nor was there ever any color change, like a bruise. I can feel something that feels almost like a rubber band that will move a little.