This happened to a flight here in the US about 10 years ago with some commentators from ESPN on it. I think one person died from their injuries, but I could be wrong on that. I know at least one person was seriously injured from hitting their head on the ceiling.
This is why they say keep your seatbelts buckled, even when cruising. Pockets of turbulence are unpredictable and can cause rapid loss of lift on the wings.