EE HAD BACKED HIS LOADED TRUCK TRACTOR OUT OF THE SHOP AND PARKED IT ON INCLINE DIRECTLY IN FRONT OF THE SHOP DOOR. HE APPLIED PARKING BRAKE AND LEFT TRUCK, THE TRUCK BEGAN TO ROLL BACKWARDS, HE ATTEMPTED TO MOUNT TRUCK TO STOP IT. THE TRUCK JACKNIFED AND HE FELL BETWEEN TRACTOR CAB AND THE TRAILER WHERE HIS ARM WAS PINCHED BETWEEN CAB AND TRAILER.