EMPLOYEE WAS USING A CASE STEER (BOBCAT). THE EE EXITED THE CAB OF THE CASE WHEN THE LANYARD FROM THE HARNESS HE WAS WEARING WRAPPED AROUND THE LT. CONTROL HANDLE CAUSING THE CASE TO ENGAGE THE LT. WHEELS, SPINNING THE EQUIPMENT AROUND CLOCKWISE. THE EE'S RT. ANKLE WAS DRAGGED UNDER THEN TRAPPED UNDER THE LT. SPINNING FRONT WHEEL. A CO-WORKER FREED THE LANYARD.