EE WAS OPERATING THE MANTRIP GOING TO THE SECTION AT THE START OF THE SHIFT, WHEN THE FRONT WHEEL APPARENTLY HIT A SMALL ROCK IN THE ROAD AND CAUSED THE STEERING WHEEL TO SPIN AND JERKED HIS ARM RATHER QUICKLY RESULTING IN A PAIN THAT HE FELT UP HIS RT. ARM. HE WORKED THE REST OF THE SHIFT, THEN WENT TO THE DR. 4-4-02.