On June 29, 2015 about 0230 eastern daylight time, a flight attendant experienced a serious injury aboard Delta Air Lines flight 74, a Boeing 767, N825MH. According to flight attendant (FA) statements, while in cruise flight with no turbulence, a FA was descending the ladder into the crew rest area when her foot slipped off a rung, twisting her right ankle. The FA continued her duties although her ankle had swelled and she was in pain. After landing, the FA was diagnosed with a broken right ankle. The FA reported that the tread was worn. The CFR Part 121 scheduled passenger flight was enroute from Atlanta, Georgia, to Amsterdam, Netherlands.