The Baltimore Orioles swept a twinight doubleheader from the Chicago White Sox, 7-2 and, 5-0, tonight but their victories were overshadowed by news of a potentially serious knee injury to their undefeated left-hander, Mike Flanagan.

Flanagan, off to a 6-0 start, twisted his left knee while trying to field a routine grounder back through the box. He was examined by an orthopedic specialist, and an arthrogram on Wednesday will determine whether Flanagan has a tear of the medial collateral ligament, which would require surgery. If it is not torn, he might be able to pitch with a brace in two weeks, although it was feared in the Orioles' clubhouse that he could be out for most, if not all, of the season.

"I think that maybe my spike caught and it twisted my knee. I felt a sharp pain immediately . . . It was a freak accident . . . I just turned the wrong way," said Flanagan in a press release. Flanagan hurt himself while twisting and lunging to his right to try to catch a grounder back through the middle by the game's second hitter, Tony Bernazard.

"What's encouraging is that I was able to get up (and limp off)," he said. "But we'll just have to wait and see with the test tomorrow . . . I've never had any sort of knee problems before."

"That certainly doesn't sound good," said Hank Peters, the Orioles' general manager, moments after hearing the inconclusive diagnosis.

The grim consensus in the clubhouse after the game was that anything less than a season-ending injury will be a minor miracle. Reliever Tim Stoddard had the same freak injury last September and all he did was take a misstep in a restaurant.

"I'm just kind of sick to my stomach and have been ever since I heard Mike scream," said Ray Miller, the pitching coach. "He's got as high a threshold of pain as anybody in the game and when you see him rolling around on the ground, you know he's hurt . . . It was awful quiet in our dugout the rest of the night.

"Then you look up in the second game and some young guy just up from the minors (Mike Boddicker) has gone out and pitched a (five-hit shutout)."

"This turns the whole thing around," said Manager Joe Altobelli, who already has Jim Palmer in the disabled list. "It doesn't look good."

"You can't trust this game. And you can't find your happiness in it," said a deeply disturbed Scott McGregor, known as "Doctor Small" to Flanagan's "Doctor Large."

"(Cal) Ripken gets hit in the head by a pitch last year and it leaves a hole in the helmet in the temple and he doesn't miss one game. Mike makes a simple little move that he's done a thousand times and he goes down. You're looking at him on the ground and you're saying, 'This can't be right.'

"This game'll make you crazy if you let it . . . The doctor said that, by the feel of it, there was a tear. I'll tell you, there's not much optimism around here.

"You see a guy who's spent three years rehabilitating himself to get back where he was (as Cy Young winner in 1979) and just as he gets there, it's all shattered. Now, he'll probably have to do it all over again," said McGregor. "I talked to him, but he was just real quiet. He's gotta be thinking about everything that could be taken away--All-Star game, another Cy Young."

Flanagan has won 13 of 14 decisions since August.

On a night when Flanagan's injury could be the Orioles' worst news of the season, everything else went their way. Sammy Stewart pitched 5 2/3 innings of excellent long relief of Flanagan and winner Tim Stoddard had three innings of one-hit shutout relief.

In the nightcap, just when the Orioles figured their bullpen would be worked to tatters, Boddicker--who had never won a major league start, much less pitched a complete game or shutout--turned in as crafty and confident five-hitter as anybody could want. Only Lenn Sakata struggled; after a zero-for-8 night, he has the incredible distinction of going zero for 60 against the White Sox in his career.

The Orioles, 21-13 and in first place in the American League East after winning six of seven, broke open a deadlocked opening game with a five-run seventh inning against Lamarr Hoyt, the league's leading winner last season. Dan Ford's looping, shattered-bat liner, which barely cleared a drawn-in infield, broke the tie; Gary Roenicke's three-run homer moments later off Jerry Koosman iced the victory.

Long, back-to-back home runs in the second inning of the nightcap by rookie Leo Hernandez (who also homered in the opener) and Rick Dempsey off Dennis Lamp gave Boddicker support for his second big league win.

For Boddicker, this night was as much a dream as Flanagan's evening was a nightmare. At 25, this is his fourth trial with the Orioles and his last. He's out of options and everybody knows it's now or never for him. "I've just kept knocking on the door," he said. "Hopefully, this time I'll stay."

Those who've regarded Boddicker, who's not a hard thrower, as a marginal major leaguer, should have seen him tonight. He walked one, struck out eight and had total command of his fast ball, fork ball and curve.

Boddicker has been living with his wife in a hotel for two weeks, not knowing what day he might be sent back to Rochester. He tried to give a mass press conference tonight, but his teammates, led by Ken Singleton, kept interrupting, saying, "You can start looking for an apartment now," and "We're canceling your reservations at the Holiday Inn," and "Call from Ronald Ray-Gun for Mike Boddicker."

Before the ninth, catcher Rick Dempsey said to Boddicker, innocently, "This will be your first shutout up here, won't it? Well, we'll strike the last guy out and I'll save you the ball."

Just to be sure, Boddicker struck out the last two batters super rookies Ron Kittle and Greg Walker. Asked who Boddicker pitched like, Dempsey said, "A right-handed Mike Flanagan."