AN MLG CAUGHT IN A MOUNTAIN WAVE WIND CONDITION RESULTED IN MINOR INJURIES TO ONE CABIN AND PAX.

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IN CRUISE AT FL330; IN SMOOTH; VMC CONDITIONS; ATC ADVISED US OF MODERATE MOUNTAIN WAVE ACTIVITY ASSOCIATED WITH LIGHT TURB AHEAD AND FOR THE NEXT 40 MI. IN PREPARATION; THE FLT ATTENDANTS WERE WARNED OVER THE INTERPHONE OF POSSIBLE CHOPPY AIR AND THE IGNITION WAS PLACED IN CONTINUOUS. APPROX 3 MINS LATER WE ENCOUNTERED LIGHT MOUNTAIN WAVE ACTIVITY WITH NO AIRSPD CHANGES AND PLUS OR MINUS 300 FPM VERT SPD CHANGES WITHIN 5 SECONDS THIS WAS FOLLOWED BY A RAPID AND VIOLENT UPDRAFT (VERT SPD AT 6000 FPM UP) WITH THE AIRSPD INCREASING RAPIDLY. THE CAPT NOTIFIED ATC THAT WE WERE UNABLE TO MAINTAIN ALT. I DISCONNECTED THE AUTOTHROTTLE; IN AN ATTEMPT TO ARREST THE AIRSPD FROM INCREASING; AND FINALLY THE THROTTLES WERE PLACED AT IDLE; AIRSPD WAS ABOUT 10-15 KTS ABOVE BARBER POLE; PITCH ATTITUDE ABOUT 7 DEGS NOSE UP AND THE ACFT WAS STILL CLBING RAPIDLY. THE CLB WAS FINALLY ARRESTED AT FL345. THE CAPT MADE A PA ANNOUNCEMENT FOR THE PAX AND FLT ATTENDANTS TO TAKE THEIR SEATS. THE CLB WAS FOLLOWED BY A RAPID DSCNT (6000 FPM DOWN) WITH THE AIRSPD DECREASING TO 230 KIAS. MY CONCERN WAS NOT TO OVER STRESS THE ACFT WITH FAST ELEVATOR MOVEMENTS. THE ACFT WAS NOW LEVELED AT FL315 AND ATC WAS ADVISED THAT WE WERE ATTEMPTING A CLB BACK TO FL330. WE ENCOUNTERED NO FURTHER MOUNTAIN WAVE ACTIVITY OR TURB. THE AUTOPLT APPEARED TO HAVE DISCONNECTED BY ITSELF DURING THE INITIAL UPDRAFT. BEFORE WE WERE ABLE TO TALK AGAIN TO ATC; ATC MADE A GENERAL ANNOUNCEMENT THAT THE MOUNTAIN WAVE ACTIVITY WAS SEVERE. THE CAPT THEN INFORMED ATC THAT THEY SHOULD NOT ALLOW OTHER ACFT TO PROCEED AT THAT ALT OVER THE SAME AREA. WE WERE THEN CLRED TO DSND TO FL290. WE RECEIVED A CALL FROM THE FIRST FLT ATTENDANT; THAT THERE WAS ONE FLT ATTENDANT INJURED AND THAT THERE WAS ONE PAX USING OXYGEN. CAPT DIRECTED THE FLT ATTENDANT TO LOCATE A DOCTOR TO ATTEND TO THE PAX AND FLT ATTENDANT; AND IT WAS SO DONE. THE COMPANY; DISPATCH; MAINT WERE NOTIFIED AND A LOGBOOK WRITE-UP WAS MADE REQUIRING A SEVERE TURB INSPECTION OF THE ACFT ON ARR WHICH WAS SO DONE. PARAMEDICS AWAITED THE FLT WHERE THE 1 PAX WAS RELEASED HOME AND THE FLT ATTENDANT WAS TAKEN TO THE HOSPITAL FOR PRECAUTIONARY X-RAYS; YET NO PROBS WERE FOUND. I BELIEVE THAT OTHER ACFT INVOLVED PREVIOUS TO US SHOULD HAVE BEEN MORE DESCRIPTIVE OF THE CONDITIONS AND ATC SHOULD HAVE USED THE WORD MODERATE TURB ASSOCIATED WITH MOUNTAIN WAVE; INSTEAD OF LIGHT.