Narrative:

We were level at FL280 with a smooth ride. The seat belt sign was off with no complaints from any other traffic. Quite suddenly; we experienced a very slight roll momentarily; followed by a couple of sudden moderate jolts. I reached up as quickly as I could to turn the seat belt sign on. We were then immediately back to smooth air again. We told ATC of our encounter and if there were any complaints out there. He responded that there were no complaints all afternoon. We did notice that there was TCAS traffic about 17 miles ahead and 2;000 ft. Above us in a crossing pattern. I can only surmise that we possibly encountered wake turbulence from that aircraft in front of us; as I have no other plausible explanation. I called the cabin to check on everybody and found that two flight attendants had been injured. Our chief purser headed to the back of the cabin to find out what happened. In a little while he called back to tell us that one flight attendant had bruised his arm or elbow during the event; and another flight attendant had a more substantive injury. During the turbulence encounter; one of the large serving carts fell over onto her foot creating an extremely painful injury.chief purser then followed protocol and solicited onboard medical personnel. He wound up with a paramedic; a nurse; and of all things; a podiatrist. They began attending to the foot injury; while the purser initiated a call to medlink from the back cabin. As they were working the problem in the back; I was giving dispatch a heads up on what was taking place. I advised that we were still waiting to find out about the seriousness of the problem; and to be prepared for a possible diversion. We finally heard back from [chief purser] and was told that [the foot] injury could be some sort of fracture but really unsure of that. We were also told that she would definitely be out of commission for the rest of the flight; with having to keep her foot elevated with ice application and ibuprofen for pain and swelling. The docs all had decided that it would probably be safe for continuing on to [destination]. I was concerned that such a long flight at high altitude could cause swelling issues and pain beyond necessary. [Chief purser] questioned her a bit more about her uneasiness to continue; and found that she had just successfully battled cancer with a routine of chemotherapy. When the onboard docs heard that; they immediately changed their minds about continuing on. They didn't want to take any chances with possible blood clotting or other complications. That then made the decision to divert quite easy and prudent. After a quick call with dispatch; we decided to divert to [a nearby airport].clearance was given right away to proceed direct to [the divert airport]. We proceeded with the diversion; and began following our own protocol with the fom [QRH] diversion guide. We also made an announcement to our passengers about what was taking place and why. At this point; we were about 30 minutes or so from [landing]; and began dumping fuel as we needed to lose 100;000lbs of weight to get down to max landing weight. There was medical personnel standing by upon landing. We blocked at gate and medical personnel came aboard right away and headed back to attend to our injured flight attendants. Both flight attendants were taken off the aircraft for medical evaluation. Many thanks to all involved for a successful outcome to this event.

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Original NASA ASRS Text

Title: B777 flight crew reported two flight attendants were injured when they encountered probable wake turbulence at FL280 from a crossing aircraft at FL300.

Narrative: We were level at FL280 with a smooth ride. The seat belt sign was off with no complaints from any other traffic. Quite suddenly; we experienced a very slight roll momentarily; followed by a couple of sudden moderate jolts. I reached up as quickly as I could to turn the seat belt sign on. We were then immediately back to smooth air again. We told ATC of our encounter and if there were any complaints out there. He responded that there were no complaints all afternoon. We did notice that there was TCAS traffic about 17 miles ahead and 2;000 ft. above us in a crossing pattern. I can only surmise that we possibly encountered wake turbulence from that aircraft in front of us; as I have no other plausible explanation. I called the cabin to check on everybody and found that two flight attendants had been injured. Our Chief Purser headed to the back of the cabin to find out what happened. In a little while he called back to tell us that one flight attendant had bruised his arm or elbow during the event; and another flight attendant had a more substantive injury. During the turbulence encounter; one of the large serving carts fell over onto her foot creating an extremely painful injury.Chief Purser then followed protocol and solicited onboard medical personnel. He wound up with a paramedic; a nurse; and of all things; a podiatrist. They began attending to the foot injury; while the Purser initiated a call to Medlink from the back cabin. As they were working the problem in the back; I was giving Dispatch a heads up on what was taking place. I advised that we were still waiting to find out about the seriousness of the problem; and to be prepared for a possible diversion. We finally heard back from [Chief Purser] and was told that [the foot] injury could be some sort of fracture but really unsure of that. We were also told that she would definitely be out of commission for the rest of the flight; with having to keep her foot elevated with ice application and ibuprofen for pain and swelling. The docs all had decided that it would probably be safe for continuing on to [destination]. I was concerned that such a long flight at high altitude could cause swelling issues and pain beyond necessary. [Chief Purser] questioned her a bit more about her uneasiness to continue; and found that she had just successfully battled cancer with a routine of chemotherapy. When the onboard docs heard that; they immediately changed their minds about continuing on. They didn't want to take any chances with possible blood clotting or other complications. That then made the decision to divert quite easy and prudent. After a quick call with Dispatch; we decided to divert to [a nearby airport].Clearance was given right away to proceed direct to [the divert airport]. We proceeded with the diversion; and began following our own protocol with the FOM [QRH] Diversion Guide. We also made an announcement to our passengers about what was taking place and why. At this point; we were about 30 minutes or so from [landing]; and began dumping fuel as we needed to lose 100;000lbs of weight to get down to max landing weight. There was medical personnel standing by upon landing. We blocked at gate and medical personnel came aboard right away and headed back to attend to our injured flight attendants. Both flight attendants were taken off the aircraft for medical evaluation. Many thanks to all involved for a successful outcome to this event.

Data retrieved from NASA's ASRS site 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.