EMPLOYEE WAS DESCENDING STAIRWAY IN THE MAINTENANCE SHOP AREA. EMPLOYEE DESCENDED DOWN THE STAIRWAY UNTIL HE REACHED THE LAST STEP LOSING HIS FOOTING & SLIPPING OFF OF THE LAST STEP STRIKING THE FLOOR RESULTING WITH A BRUISED LEFT KNEE & SORE BACK ON HIS LEFT SIDE. EMPLOYEE ALSO STATED THAT HIS LEFT SIDE RIBS HURT. EMPLOYEE WAS SENT TO VRMC TO BE CHECKED OUT.