EE WAS PERFORMING ROUTINE MAINTENANCE DUTIES. HE RAN OUT OF CLEAN CLOTHS AND ASKED A CO-WORKER TO HAND HIM SOME. CO-WORKER CAME DOWN STEPS & INJURED CAME UP STAIRWAY TO MEET HIM. INJURED START ED TO DESCEND STAIRWAY. ON HIS FIRST STEP BACKWARDS HE EITHER MISSED A STEP OR SLIPPED. HE STARTED TO FALL & CONTINUED UNTIL HE LANDED ON THE BOARDING PLATFORM BELOW(APPROX 4 FEET). STRAIN/BR