EMPLOYEE WAS EXAMINED AT E.R. & X-RAYS WERE NEG. EE SAID HIS NECK WAS BOTHERING HIM SO HE WENT TO THE CHIROPRACTOR ON 4/7/04. EE WAS OPERATING HAUL TRUCK ON MUDDY GROUND WHEN TRUCK DROVE INTO DEEP RUT & CAUSED EE TO ROCK BACK & FORTH IN CAB & STRIKE LT.SHOULDER IN CAB.