Narrative:

Event: 2 flight attendants experienced minor injuries from a 2-4 second moderate turbulence jolt during smooth to occasional light chop at FL280. PA announcement used at onset to have flight attendants seated. Injuries, bruises and muscle/joint soreness, did not require first aid in-flight (other than an aspirin) or medical attention upon arrival. 2 supervisors met flight on arrival and were debriefed by purser and affected flight attendants. Leading up to event: talked to dispatch during flight planning to change route and altitude away from forecast SIGMET turbulence in area FL300-380. Dispatch had no reports of the turbulence in the area and told us there were other company flts going ahead of us. We chose to fly at FL290 until clear of SIGMET area. Other company flts were ahead of us on same track but higher (FL340 and up) and we were communicating with them. They were experiencing light to moderate chop with occasional moderate jolts. Air carrier Y was above and just ahead of us with light chop to light turbulence. To be on the safe side we descended to FL280 and kept the passenger seatbelt sign on. The flight attendants had been briefed that this area would have intermittent turbulence and to be ready to be seated with a PA announcement. Every precaution, short of having the flight attendants strapped in during smooth air and chop for 2.5+ hours, was accomplished.

Related reports:

Google
 

Original NASA ASRS Text

Title: A B777 ENCOUNTERS MODERATE TURB RESULTING IN MINOR INJURIES TO 2 FLT ATTENDANTS.

Narrative: EVENT: 2 FLT ATTENDANTS EXPERIENCED MINOR INJURIES FROM A 2-4 SECOND MODERATE TURB JOLT DURING SMOOTH TO OCCASIONAL LIGHT CHOP AT FL280. PA ANNOUNCEMENT USED AT ONSET TO HAVE FLT ATTENDANTS SEATED. INJURIES, BRUISES AND MUSCLE/JOINT SORENESS, DID NOT REQUIRE FIRST AID INFLT (OTHER THAN AN ASPIRIN) OR MEDICAL ATTN UPON ARR. 2 SUPVRS MET FLT ON ARR AND WERE DEBRIEFED BY PURSER AND AFFECTED FLT ATTENDANTS. LEADING UP TO EVENT: TALKED TO DISPATCH DURING FLT PLANNING TO CHANGE RTE AND ALT AWAY FROM FORECAST SIGMET TURB IN AREA FL300-380. DISPATCH HAD NO RPTS OF THE TURB IN THE AREA AND TOLD US THERE WERE OTHER COMPANY FLTS GOING AHEAD OF US. WE CHOSE TO FLY AT FL290 UNTIL CLR OF SIGMET AREA. OTHER COMPANY FLTS WERE AHEAD OF US ON SAME TRACK BUT HIGHER (FL340 AND UP) AND WE WERE COMMUNICATING WITH THEM. THEY WERE EXPERIENCING LIGHT TO MODERATE CHOP WITH OCCASIONAL MODERATE JOLTS. ACR Y WAS ABOVE AND JUST AHEAD OF US WITH LIGHT CHOP TO LIGHT TURB. TO BE ON THE SAFE SIDE WE DSNDED TO FL280 AND KEPT THE PAX SEATBELT SIGN ON. THE FLT ATTENDANTS HAD BEEN BRIEFED THAT THIS AREA WOULD HAVE INTERMITTENT TURB AND TO BE READY TO BE SEATED WITH A PA ANNOUNCEMENT. EVERY PRECAUTION, SHORT OF HAVING THE FLT ATTENDANTS STRAPPED IN DURING SMOOTH AIR AND CHOP FOR 2.5+ HRS, WAS ACCOMPLISHED.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.