EMPLOYEE WAS DESCENDING THE LADDER OF CAT TRUCK TO INSPECT AREA. THE AREA WAS DARK AND HE DID NOT REALIZE STEP TO GROUND WAS MORE THAN NORMAL. EMPLOYEE FELL BACKWARDS INJURING RIGHT ARM, WRIST, NECK AND BACK. HE DID NOT REPORT TO SUPERVISOR UNTIL 11-8-05. INITIALLY TREATED AS 1ST AID. ON 2ND VISIT TO DOCTORS 11-9-05 CHANGED TO REPORTABLE DUE TO MEDICATION PRESCRIBED.