B737-800
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 261
Flight Deck / Cabin / Aircraft Event Illness / Injury; Inflight Event / Encounter Wake Vortex Encounter
General Physical Injury / Incapacitation
Environment - Non Weather Related; Procedure
We were just about to start our descent into LAS. I believe we were at FL340. We heard ATC report that we had traffic (a B777) at 12:00; 1000 ft below us. We responded that we were looking. What we saw was a Boeing 747; 1000 ft above us and off to our left by a mile or so. Rides at this time were smooth and the Flight Attendants were up; however; I had the seatbelt sign on with the passengers in their seats. Approximately two to three minutes later; we ran into what felt to us as moderate turbulence with a roll both left and right. In my opinion it was wake turbulence. As soon as we were out of it (only a few seconds); I called back to check on the Flight Attendants. They said they were okay. We continued our approach and made a normal landing in LAS. After we got to the gate the C Flight Attendant came up and told me she had hit her back on the counter of the aft galley. She said she was okay but had some bruising below her shoulder blade.
B737-800 Captain reported encountering wake turbulence from a B747 in the LAS area that resulted in minor injuries to a Flight Attendant.