According to the captain of the flight, at the time of the turbulence encounter he was navigating around scattered cloud build-ups. Nothing was showing on radar. The injured flight attendant stated that she was walking down the aisle between the mid galley and the aft galley and fell to the floor at the time of the turbulence encounter. According to the operator, no turbulence was forecast for the area in which the airplane was flying at the time of the turbulence encounter. In addition, satellite imagery revealed that the airplane was in an area not conducive to turbulence when the event occurred. According to the flight data recorder, the vertical acceleration during the turbulence encounter varied between 1.5 g and -0.3 g. The encounter lasted about 5 seconds. Probable Cause: an inadvertent encounter with clear air turbulence.