At the end of shift, EE parked haul truck at the access platform located on E. side of shop. The EE was walking down the stairs and caught his rt. heel on the edge of the 2nd to last step causing his rt. ankle to roll/twist and stumbled to ground. On 9/19 an X-ray revealed a closed fracture of the right ankle. The EE was given a walking boot, crutches and placed on restrictions.