Date: 201902
Local time of day: 1201-1800
Location: ZAU.ARTCC, IL
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZAU
ATC / advisory: Center ZAU
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Inflight Event / Encounter Wake Vortex Encounter; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; General Physical Injury / Incapacitation
Contributing factors: Environment - Non Weather Related; Procedure
Primary problem: Ambiguous

Narrative: During cruise we encountered two to four seconds of wake turbulence/moderate turbulence. Prior to incident; during climb and cruise; conditions there were occasional light chop with ATC (MDW and IND ARTCC) reporting the same ahead of us. During climb; I had authorized F/As (Flight Attendants) to get up to conduct a water service and then clean/secure the cabin for anticipated turbulence projected for the last third of flight. When encountered; I made a PA immediately for the F/As to take their seats. Afterwards we contacted F/As to check on their status. We were informed that the C F/A had fallen to the floor; injuring her back. When queried; she informed me she was in a lot of pain and could not continue her duties. She then told me she was going to apply ice and take ibuprofen for the pain. I discussed with her about contacting Stat-MD and she felt it was not necessary. I discussed with the F/O (First Officer) that we would check on her status in ten minutes and if no improvement; then contacting Stat-MD. When I checked with her after ten minutes; she informed me that the ice and ibuprofen had helped but she still did not feel well enough to continue her duties. I instructed her to stay seated and we would have EMS meet the aircraft. During this process; Dispatch was notified of situation; to contact EMS to meet aircraft; and notify F/A scheduling. Arrival; landing; and taxi to gate were uneventful. Passengers were kept seated while EMS came on board and assisted her off the aircraft. We talked with her in terminal and suggested she go to local hospital to be completely evaluated (EMS did not have facilities to do so). She declined; choosing to go home and be evaluated there. After the initial turbulence encounter; we did not encounter any more moderate turbulence; along with the short duration; leads me to believe what we encountered was due to wake turbulence.


Second narrative: During cruise we asked ATC for a ride report. We were told to expect occasional light chop. Shortly thereafter the Captain asked me to relay to the cabin crew that he would like them to do a water only service. A couple minutes later we hit what felt like two distinct wake turbulence bumps followed by a third a couple moments later. I would characterize them as strong light to weak moderate. A few moments later; one of the crew called up to inform us that our C Flight Attendant had injured her back.


Synopsis: B737-700 flight crew reported encountering probably wake turbulence in cruise flight at FL260 that resulted in a minor injury to a Flight Attendant.