A B737-500 CAPT RPTED THAT HE DID HIS BEST TO AVOID TURB; BUT A FLT ATTENDANT WAS INJURED ANYWAY IN SCT'S AIRSPACE. HE DID NOT FIND THIS OUT UNTIL SUBSEQUENTLY DEPARTING ON THE SECOND LEG.

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IT WAS THE FIRST LEG OF THE DAY FOR ALL CREW MEMBERS. THE DISPATCH RELEASE INDICATED 2 REMARKS: 1) OCCASIONAL MODERATE CHOP LESS THAN 10000 FT AND 2 MI; AND 2) OCCASIONAL MODERATE CHOP FL180-FL380. I INCLUDED THIS IN MY BRIEFING TO THE FLT ATTENDANTS. THE INBOUND CREW CAME FROM SAN AND INDICATED EVERYBODY WAS BAILING OUT OF THE HIGH ALT SECTOR DUE TO THE POOR RIDE CONDITIONS IN SOUTHERN CALIFORNIA. HOWEVER; ZOA SAID THERE WERE NO COMPLAINTS; SO WE CLBED TO FL370 AND EXPERIENCED A SMOOTH RIDE. ADDITIONALLY; THERE WERE NO RPTS OF MODERATE CHOP FROM ZLA OR SOCAL FOR THE REMAINDER OF OUR FLT. NONETHELESS; I ELECTED TO SECURE THE CABIN EARLY AT APPROX 15000 FT AS A PRECAUTIONARY MEASURE. SOCAL VECTORED US FOR A L DOWNWIND FOR RWY 8L. AT APPROX 6000 FT ON A VECTOR HDG OF 260 DEGS; AND NOT YET CLRED FOR THE VISUAL APCH; WE HIT UNEXPECTED CLR AIR; OCCASIONAL MODERATE CHOP WITH DURATION OF ABOUT 1 MIN. I BROKE L; AWAY FROM THE MOUNTAINS; TO ESCAPE IT ASAP; INFORMED SOCAL OF THE ENCOUNTER AND WE WERE SUBSEQUENTLY CLRED FOR THE VISUAL APCH WITH A RESTR TO TURN BASE AT OR ABOVE 4000 FT AND TO TURN FINAL AT OR ABOVE 3000 FT. ALTHOUGH I PRESUMED THE FLT ATTENDANTS WOULD HAVE SECURED THE CABIN BY THE TIME OF THE TURB ENCOUNTER; THEY WERE ACTUALLY JUST FINISHING UP. 'B' FLT ATTENDANT FELL OFF HER JUMPSEAT AND WAS INJURED. AFTER THE FLT; SHE COMPLAINED OF SOME NECK PAIN; BUT THOUGHT SHE MIGHT BE ALRIGHT AFTER TAKING SOME IBUPROFEN. UNFORTUNATELY; DURING THE SUBSEQUENT FLT; THE OTHER FLT ATTENDANTS REALIZED SHE WAS STILL IN TOO MUCH PAIN TO PERFORM HER DUTIES WELL. CONSEQUENTLY; WE COORDINATED WITH (WHILE IN LONG RANGE) SCHEDULING TO HAVE HER REPLACED. SHE DID NOT WISH TO BE CHKED OUT BY PARAMEDICS. HOWEVER; A FLT ATTENDANT SUPVR MET THE PLANE AND ESCORTED HER TO HIS OFFICE TO PUT AN ICE PACK ON THE INJURY WHILE SHE AWAITED A FLT HOME.