Date: 201504
Local time of day: 1201-1800
Location: EGTT.ARTCC, FO
Flight conditions: VMC
Light: Daylight
Aircraft: B767-300 and 300 ER
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
ATC / advisory: Center EGTT
Second aircraft: B777 Undifferentiated or Other Model
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: First Officer; Pilot Flying
Anomaly: Inflight Event / Encounter Wake Vortex Encounter; Inflight Event / Encounter Loss Of Aircraft Control
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Regained Aircraft Control; General Physical Injury / Incapacitation
Contributing factors: Environment - Non Weather Related; Procedure
Primary problem: Environment - Non Weather Related

Narrative: We departed London and had just reached our cruising altitude of FL320. It was VMC and we had asked ATC for ride conditions. They advised smooth; no complaints.  Seat belt sign was on.  All of a sudden we received two violent jolts; rolling the aircraft up and to the right. There were negative g's and objects thrown around.  It was sudden and with no warning.  We heard objects being thrown about in the back. Airspeed increased and aircraft was thrown in pitch up and roll; twice. Asked ATC about separation and advised we had a wake turbulence encounter.  They had just turned us with a heading off of the airway.  They advised we were approximately 12 miles behind and 2200 feet below a 777. We advised that we needed more separation and also informed them we had injuries.  No traffic showed on TCAS - probably because he was greater than 2000 feet above.   After we were assured aircraft was under control and we were separated from the threat; I called back to check on the flight attendants (FA).  They were all shaken up; but one FA in the rear had a cart land on her when it came back down; hitting her knee. Advised dispatch and medical.  FA was relieved of duties for the remainder of flight; and seated with her leg elevated and the knee covered in ice.  Her shoulder and neck hurt as well; but the knee was the worst.  There was no sign of bleeding or torn skin; but it was clearly banged and swelling larger than the other knee.    Asked [Dispatch] to bring [Maintenance] in on the line.  Asked [Manager] if we were legal to continue and enter ETOPs airspace after a severe turbulence encounter; explained we had the two bouts of negative g's.   [Manager] advised he would check; and got back to us with an ACARS message explaining he had checked with the fleet; and wake turbulence encounter was not severe turbulence.  Based on this clarification made the logbook entry 'wake turbulence encounter'.  Also made logbook entries for the medical kit being used. FA was being met by her husband anyway at destination; and stated she would prefer to go to [Company] clinic with him; than to be met by paramedics.  Asked [Dispatch] if they could verify if clinic would be open when we arrived; but they never got back to us.   An FA supervisor met the flight and we explained the situation to him.  Lead FA did an excellent job and the injured FA had a very good attitude.


Second narrative: [Report narrative contained no additional information]


Synopsis: B767 flight crew reported encountering wake turbulence at FL320 in trail of a B777 departing EGLL that resulted in injuries to a Flight Attendant.