Boeing Co 747-400, VH-ANA

The pilot in command of the Boeing 747 reported that while
cruising at flight level 380 the aircraft encountered clear air
turbulence. Although the weather forecast indicated active
thunderstorms within 110 NM of the track being flown, turbulence
was not forecast nor was there any indication, either visually or
via the radar, that turbulence was imminent. The seat belt sign was
not illuminated at the time, nor was it required to be
illuminated.

Cabin crew reported that a passenger sustained a suspected
broken ankle while exiting a lavatory. Another passenger, who was
waiting to enter a lavatory, sustained a suspected sprained ankle.
There were no other reports of injuries.