EMPLOYEE WAS TRYING TO GET S/C ON THE OUTBY SIDE WHILE IT WAS LOADING. HE TRIPPED ON TRAILING FALLING DOWN. WHEN EE GOT BACK UP ON HIS FEET THE S/C BEGAN TO TRAM TOWARDS THE FEEDER, STRIKING HIM ON BOTH LEGS BELOW THE KNEE, KNOCKING HIM ON HIS BACK. EE GRABBED ONTO THE BUMPER OF THE S/C DRAGGING HIM APPROX. 5' BEFORE STOPPING.