All he remembers feeling while lying on the semi-truck trailer’s steel floor was someone pounding his knee with a hammer. Andrew Ellis had just rolled into a little town outside San Antonio to drop off a load at a hardware store. He was using a two-wheel dolly to unload a bundle of PVC pipes from the truck bed when, as he was pulling with full force, the pipes slipped and the laws of gravity sent Ellis tumbling backward. He could feel his left knee pop. He thinks the laces of his boot may have caught a rivet as he was on his way down, causing the joints in his knee to contort out of place — but he isn’t 100 percent sure.