Played by the rules, basketball is the prettiest game. It is ballet in short pants. But the NBA has made it ugly. By condoning nearly any physical contact short of decapitation, the professionals seem doomed to become hockey players without ice. And who needs more fist-fights on the nightly news?

You've seen the fights. All winter, the Washington television stations played a short film clip of the latest hockey game at Capital Centre. The clip usually showed a fistfight. It is significant to know the TV stations didn't shoot those films; they were provided by the hockey people, who have moved beyond condoning violence to selling it.

You've seen the fights. You've seen the hockey players thro down their gloves and put up their fists. You've seen them circling each other, waiting to throw a good right hand. And where were the referees, those protectors of law and order? They stood in the background. They watched. They tried to stop the fight only after it was well under way. Peace sells no tickets.

That is sick. Hockey is a wonderful game, offering great rewards for precise teamwork. On the fly, a skater with the puck moves witnesses to joy. Against that assault stands the goalic, whose courage must be surpassing. That is the game at its simplest, but its most beautiful moments, when it is kaleidoscopic in its changing patterns, come when the puck moves from stick to stick in search of a crack in the shifting defense.

And the hockey people shoot film of the fist-fights.

To its credit, basketball dosen't sell war. The commissioner, Larry O'Brien, has taken strong measures to prevent it. This season, he fined a player $10,000 and suspended him 60 days; another he fined $5,000. Since those fines, O'Brien said yesterday, his office has received fewer reports of physical incidents.

Best of all, the NBA may be ready to do away with hand-checking.

Hand-checking has defiled the game's beauty. Mikhail Baryshnikov is a leaper, all right, but could he do it if Nureyev bopped him at the hip with the heel of his hand as he moved to jump?

Who wants to see Elvin Hayes lean agianst Jack Sikma tonight? At $8 a pop, a ticket holder is entitled to see Hayes move - no one so big ever moved so garcefully - without, Sikma jumping on his back and going along for the ride. What fun is there in seeing Hayes back up, jerking backward as if bumping into a wall again and again, while Sikma pushes and shoves him forward? For $8, we can see pro rasslers in masks if we go for bumpations.

Worse than that, hand-checking leads to fights. BY allowing defenders to put their hands on the offensive men the NBA is saying such hand-checking is all right as long as it doesn't get too bad. But what, pray tell, is "too bad?" And isn't it human nature that a little friendly hand-checking can, in the heat of battle, turn into aggressive shoving or even punishing licks? If you're a defender, you go as far as you can (while the referee is looking, that is; when he turns his head, you make the hand-check a forearm shiver).

In virtually every NBA fight, the excuse for the fisticuffs is the same. "He did it first, but I retaliated and you saw me."

They're all talking about hand-checking.

Nowhere in the rule book does it say the defender can put his hands on the offensive player. On the contrary, that's supposed to be a punishable foul. Sometimes permitted in college games - a melancholy product of the pros' dissipation - hand-checking can change the character of basketball, making the game a test of strength more than of grace.

O'Brien, in town for tonight's second game of the NBA championship series, said, "It's clear something has to be done to control this hand-checking. Possiblily eliminate it . . . It's happening all over the floor, it's happening away from the ball. It becomes more vigorous until it's not basically hand-checking anymore; it's more physical. And that leads to the ultimate confrontation."

O'Brien won't say what he thinks must be done about hand-checking. An ad hoc committee of NBA owners is stuyding the problem and will make a recommendation at the annual league meetings beginning June 12 at San Diego. At the same time, the NBA will discuss, for a fourth year, the possiblilty of using three officials in games (the extra man ostensibly could inhibit away-from-the-ball hijinks).

Adding a third official to the current 26 two-man teams, O'Brien said, would cost the league perhaps $750,000 a year.

"We can't overlook the cost," the commissioner said. "Our committees will have to show the owners there is a dire need for a third official in order to justify that expenditure".

The NBA does not need a third official at every game. It simply needs to play by the rules. No man may put his hands on a player. Just tell the referees to call the fouls. Use the $750,000 for an office picnic.