A B777-200 ENCOUNTERS MODERATE TURB RESULTING IN A CABIN ATTENDANT INJURY.

Narrative

DURING DSCNT TOWARD ORD; IN VMC; I OBSERVED RADAR WX RETURNS THAT WERE APPROX 20 MI E OF ORD. BECAUSE OUR FLT WOULD TAKE US INTO THIS AREA; I CALLED THE PURSER AND DIRECTED HER TO HAVE ALL FLT ATTENDANTS TAKE THEIR SEATS; AND TO DO THE 'PREPARE FOR LNDG' WORK FROM THEIR JUMP SEATS IF THE ANTICIPATED TURB WOULD MAKE IT UNSAFE TO GET UP. SEAT BELT SIGN HAD BEEN ON FOR SEVERAL MINS. NO RPTS OF TURB FROM ATC. THE FO WAS FLYING DURING THIS DSCNT TO 10000 FT; SPD 320 KTS ASSIGNED BY ATC. IN PREPARATION FOR TURB ASSOCIATED WITH THE RADAR RETURNS; HE WAS REDUCING SPD TOWARDS 280 KTS AT ABOUT 12000 FT. STILL VMC; I OBSERVED WHITE CUMULOUS CLOUDS WITH TOPS TO ABOUT 16000 FT AHEAD; WELL SEPARATED FROM THE AREA OF RADAR RETURNS. THESE CLOUDS DID NOT HAVE ANY OF THE APPEARANCES OF SIGNIFICANT TURB; DID NOT APPEAR TO BE GROWING; ROLLING; DARK; OR OTHERWISE SUSPICIOUS. BUT WHEN WE ENTERED THE CLOUDS; WE EXPERIENCED A VERY SUDDEN DOWN/UP JOLT OF MODERATE TURB. NOT SUFFICIENT TO BE A STRUCTURAL PROB; BUT I WAS IMMEDIATELY CONCERNED ABOUT THE SAFETY OF THE FLT ATTENDANTS. SHORTLY AFTER; THE PURSER CALLED TO SAY THAT A FLT ATTENDANT HAD BEEN INJURED DURING THE JOLT; STRIKING HER HEAD ON A GALLEY CART. I DIRECTED OUR RELIEF PLT TO NOTIFY DISPATCH OF THE INCIDENT AND HAVE MEDICAL ASSISTANCE MEET THE AIRPLANE. UPON ARR; PARAMEDICS MET THE ACFT AND TOOK THE INJURED FLT ATTENDANT TO THE HOSPITAL; WHERE SHE WAS TREATED AND RELEASED.