Sammy Stewart can't even spell what's the matter with him. Infra-patella tendinitis, the doctors say. Basketball players who get it have to quit the game. One baseball pitcher who has it has been sent here on rehabilitative leave.

Stewart, one of the best relief pitchers in baseball the last few years, hasn't pitched in a game since June 22 against the Cleveland Indians, when the pain in his right knee so hindered his motion that the Baltimore Orioles had to place him on the 21-day disabled list. At the time of his injury, Stewart had worked into the starting rotation and was 5-5 with an earned run average of 4.54.

The Orioles now are in California on the western swing of a road trip. Stewart is here with their farm team, learning how to pitch again, trying to regain the confidence that gave him the league's second-lowest ERA last year. The pain is gone in his once-inflamed knees; now he must adapt to the few subtle changes he's had to make in his delivery to keep the injury from recurring.

He hopes to rejoin the Orioles late next week. But until then, he is a Hagerstown Sun, whether he likes it or not. And he doesn't seem to mind.

Of course, in his case it's a little easier. For Stewart, being a Sun means pitching 15 minutes of batting practice Monday, three innings Wednesday night against Carolina League-leading Durham and six innings Saturday against Winston-Salem near his home town of Swannanoa, N.C.

The rest of this week he will commute between here and Baltimore, where he receives two hours of therapy on his knees twice a day. And he will fly down to the game Friday; his "teammates" will take a six-hour bus ride.

"When you get to be a professional athlete, you expect to deal with some pain, but I guess I was never as really concerned about the mechanics of my body as I should have been," said Stewart, 27, who had always dismissed his chronically tender and aching knees with a shrug.

Until he went to see a specialist in Baltimore, Stewart said he never realized that his right leg is half an inch shorter than his left leg, a condition that led him to unwittingly favor his left leg and eventually caused both knees to become inflamed.

But, Stewart said, he is fortunate that his affliction was diagnosed before any harm came to his arm.

"We definitely got it in time. I haven't hurt my arm from compensating for it," he said. "If I hadn't been so lucky, I might have ended up like Mark Fidrych. When you start favoring one thing, that's where you wind up getting in trouble."

This is the big time for Hagerstown. Stewart spent as much time signing autographs as he did throwing batting practice Monday afternoon. His actual debut for the Suns Wednesday is sure to draw the 5,000-plus fans it takes to fill cozy Municipal Stadium. An added fillip for Hagerstown fans will be the professional debut of Joe Kucharski, the Orioles' No. 1 pick in the recent free-agent draft. Kucharski, a right-hander from Clinton, Md., who graduated from Surrattsville High, will relieve Stewart.

But Stewart concedes they might not get what they come for. "I'm going to be aggressive and go like it's the last time I might ever pitch. I'm going to give it 100 percent Wednesday, take it as serious as any game, but I don't know," he said Monday while peering at the outfield wall, which seems fearfully close because it is covered with dozens of gaudy advertisements.

"These guys are professionals who got signed like everybody else. I respect them. I just hope they respect me."

The Suns maintained a respectful distance as the gimpy-legged Stewart gingerly warmed up among the potholes in the Municipal Stadium outfield on Monday, his first official day as a Sun. They spoke in reverent whispers, consciously ignoring their newest teammate. But by the time Larry Sheets hit a second pitch over the 375-foot sign in center field, their awe had dissipated.

"Uh oh, that didn't take long," taunted the Orioles' minor league catching instructor, Dave Skaggs, from the sidelines.

Stewart tossed his head back and laughed. He popped the ball off his bicep and watched it roll down to his hand, one of the favorite tricks in his showman's bag. "Here comes a slider," he said, making a snapping motion with his wrist. Then he sent the ball dipping over the outside corner of the plate past a lunging Sheets.

Appropriately enough, Stewart wore his Orioles' road uniform, the red-orange 53 stitched across the back. His cap was tilted back at the same jaunty angle. Beneath the bushy walrus mustache, his jaws worked the wad of gum as furiously as ever.

But on both knees Stewart wore braces. And in his shoes he wore orthopedic lifts.

He worked easily, giving Sun catcher Dave Falcone a good look at some major-league sliders and curve balls that the Sun hitters could manage only feeble swings against.

He had a good time, but not too good a time. He is determined that this will not be his Waterloo, or as in Fidrych's case, his Pawtucket.

"You can't have all good years," he said. "Ken Singleton has hit .167 for half the year before and come back to hit .300. That's what I'm looking to do."

But even with his rejuvenated faith, there's one thing that has Stewart worried.

"I'm going to have to scrape me up a 'uni' (uniform) somewhere before Wednesday's game. Geez, I sure hope they have a number 53. Yeah, I sure do."