THE OPENING ceremonies of the Olympic Games are always a marvelous sight -- full of pageantry, music, stirring words and strong, young athletes. Yesterday's ceremonies at Lake Placid were no exception. But if the mood of this Olympiad seems different from that at other Games in other places, it is probably because this may be the last of these great spectacles.

Despite all the reassuring and self-glorifying words that have flowed from the meetings of the International Olympic Committee in recent days, the Olympic Games are in trouble. A careful observer, even one watching via television, will have little difficulty in the next 10 days figuring out why.

First, of course, there is politics. The Games, according to the men who run them, are free of this Great Vice. But conspicuous by their absence from yesterday's parade of athletes were the Chinese from Taiwan. The flag behind which their oldest brothers and sisters had marched in similar parades since 1952 and behind which they insisted they march this year is no longer acceptable to the self-perpetuating body that controls such things. Were the 27 athletes thus denied their chance at an Olympic medal because they were putting a phony principle above performance? Or were they the victims of international politics?

This group of Chinese is not the first to fail to reach the Olympic starting line for reasons that have nothing to do with sports. The Olympic Games are drenched in politics -- from the selection of the site through the judging of individual events to the closing ceremony. A few photos of the heavy security arrangements at Lake Placid will make the point if it is not already obvious -- will make it, that is, to all but the men who run the Olympics and steadfastly refuse to recognize the political implications of their own acts and decisions.

But the intrusion of politics is not the only flaw on display this year. The late Avery Brundage, that old curmudgeon who dominated the Olmpic movement for so long, did not hate the winter Games without reason. They carry the diseases of professionalism and commercialism, the two ills the guardians of the Olympic flame dread far more than mere politics.

The rules created to stamp out these evils have always been something to snicker about and evade. Are the Russian hockey players any less professional because their salaries are paid by the Soviet government than, say, the Washington Capitals, whose salaries are paid by Abe Pollin? Is the American athlete who has already hired an agent to handle anticipated post-Olympic offers cashing in on "amateurism"? Are the "official" objects about which we will hear much and often -- cars, motor oil, tires, thermal underwear, cold remedies, etc. -- any less commercial because they are endorsed by Olmypic organizers instead of by Olympic athletes?

It is too bad that what could have been the world's greatest athletic festivals have been tainted by these things. If a Soviet-American confrontation obliterates the Games as we have known them -- as well it may -- this will be because they were already so vulnerable. Any group that deceives itself so consistently about the events that swirl around it, as the IOC has done since at least the Berlin Games in 1936, has a limited life expectancy. What will be said at Lake Placid in the next few days is likely to make clear why the end is so near.