On 9/10/13 a fuel/lube tech was standing on the right side bumper of a FE loader assisting the operator to bleed the fuel system. The operator's hand slipped while spinning the fuel filter. The fuel/lube tech was bumped, causing him to fall off the bumper (approximately 4') to the ground. On 10/22, the fuel/lube tech had a medical procedure that makes this incident reportable.