On May 14, 2016, at about 1900 EDT, American Airlines flight 762, an Airbus A320, N103US, during descent into Philadelphia International Airport (KPHL), Philadelphia, Pennsylvania, a flight attendant received a serious injury while trying to put his jump seat down during turbulence.ÿ Of the 136 passengers and 5 crew members on board only the flight attendant was injured.ÿ The flight was operating under 14 Code of Federal Regulation part 121 as a scheduled passenger flight from Chicago O’Hare International Airport (KORD), Chicago, Illinois. ÿÿ During the descent into KPHL, the flight crew notified the flight attendants and made a public address announcement that there might be possible turbulence.ÿ According to the flight crew, there were no pilot reports of any turbulence ahead and there were no cells noted on the weather radar.ÿ Shortly after making the announcement,, the flight experience moderate chop for a minute or two and the flight crew reduced airspeed and advised ATC of the moderate chop.ÿ The C flight attendant was sitting down in his aft jumpseat when the turbulence was encountered, and was tossed him into the air and back down, causing him to crush his left hand in the jumpseat. The fight crew was informed of his injury and they coordinated to have medical personnel meet the airplane upon arrival in KPHL.ÿ The injured flight attendant was transported to the hospital and diagnosed with a broken left hand. Probable Cause: an inadvertent encounter with clear air turbulence that resulted in a serious injury to a flight attendant.