EMPLOYEE WAS WALKING DOWN A STEEL STAIRWAY WHEN HE SLIPPED & FELL BACKWARDS. THE STEPS WERE WET FROM RAIN THAT WAS FALLING & THE WORKERS BOOTS HAD MUD ON THE SOLES. HE GRABBED THE HANDRAIL TO STEADY HIMSELF & STRAINED HIS BACK. THE EE DID NOT ASK FOR MEDICAL ASSISTANCE UNTIL THE MORNING OF 7/02/04 & WAS PRESCRIBED MEDICATION & PHYSICAL THERAPY.