EMPLOYEE ENTERED RUTS IN HAUL ROAD CAUSING TRUCK TO ROCK BACK & FORTH. EE'S LT. THUMB WAS CAUGHT IN STEERING WHEEL & FELT STRAIN IN BACK. EE WENT TO CHIROPRACTOR WHO TOOK HIM OFF WORK FROM 7/27/04 TO 8/4/04. HE HAS NOT RETURNED TO REGULAR DUTY DUE TO RESTRICTIONS.