On December 13, 2016, at 1847 mountain standard time, United Airlines flight 1545, a Boeing 737-800, N24202, experienced turbulence during descent that resulted in one flight attendant sustaining a serious injury. There were no injuries to the other passengers and crew onboard and the airplane was not damaged. The flight was operating under the provisions of 14 Code of Federal Regulations Part 121 as a regularly scheduled passenger flight from San Francisco International Airport (SFO), California to Denver International Airport (DEN), Colorado. The flight landed at DEN with no further incident. According to the operator, weather forecasts indicated that mountain wave turbulence was expected over the Sierra Nevada mountains and moderate turbulence was forecast for the descent in to DEN below 17,000 feet. As the airplane descended through approximately FL270 the captain advised the flight attendants "it's going to get bumpy" and to be seated. The flight crew reported that passing through approximately FL220 the airplane experienced increasing turbulence and then at about FL200 experienced a "big jolt." The flight attendant in position 2L was securing the galley at the time of the turbulence and was thrown to the ceiling and then struck her face on the galley counter while falling to the floor. She suffered multiple injuries including a large gash to her cheek and a fractured facial bone.