I worked as a UPS Driver Helper for about two weeks in the old style truck, and for the first time in my life I'm experiencing a lot of knee pain. It was to the point that I had to take pain relievers throughout the day to keep going. Even my driver noticed that my running turned into a very forced brisk walk. Before this, I was a healthy person who never experienced pain. In fact, I sort of thought people that did were just complainers. Now I know what knee pain is like. Are these problems common among UPS workers?