Bjorn Borg's tender right knee, John McEnroe's gimpy left ankle, and the rigors of playing on unforgiving hard courts in 95-degree heat were the major topics of conversation today as the $654,000 U.S. Open tennis championships began with a flurry of activity and few surprises.

Borg and McEnroe, the favorites to contest the men's singles final on Sept. 7 despite niggling injuries that have caused them misgivings, easily won their first-round matches against opponents clearly uncomfortable on the rubberized asphalt courts on the National Tennis Center.

Borg, who has won five French Opens and five Wimbledon titles and now rates a first U.S. Open crown as his chief professional priority, showed inhibitions or lack of mobility in trouncing Argentinian left-hander Guillermo Aubone, 6-1, 6-4, 6-1.

McEnroe, the defending Open champion who has played indifferently this summer since losing to Borg in a magnificent Wimbledon final that generated interest far beyond the ranks of confirmed tennis buffs, bickered with a few hecklers in the stadium crowd while dispatching Frenchman Christophe Roger-Vasselin, 6-3, 6-4, 6-1.

The top women who played today -- Chris Evert Lloyd, who monopolized the Open title from 1975 through 1975, and Tracy Austin, who dethroned her in last year's final to become the youngest champion in the tournament's history -- also won their openers in straight sets.

Evert Lloyd scalded fellow Floridian Kim Sands, 6-0, 6-0, in the afternoon heat that turned Louis Armstrong Stadium into a cauldron.

In the cool of the evening, Austin scored a desultroy 6-2, 7-5 victory over Texan Anne Smith, who, like Sands, is an athletic player and former high school basketball star.

Evert Lloyd and Austin concentrated fully on tennis in their youths, and became the most consistent baseline players of the modern era. Today they forced their opponents into baseline duels they could not possibly win.

Austin has been working hard to improve her cream puff serve, but couldn't demonstrate her new velocity tonight. She is still hampered by the tightness in her right arm that troubled her last week when she lost to 15-year-old Andrea Jaeger -- the first time Austin, 17, has ever lost to a younger player.

In the last match of the night, No. 8 seed Eddie Dibbs survived two match points at 3-5 in the third set and came back from seemingly certain elimination to beat recently rejuvenated veteran Bob Lutz, 5-7, 2-6, 7-5, 6-0, 6-2.

Winner of back-to-back hard court tournaments in Columbus, Ohio, and Stowe, Vt., earlier this month, Lutz was serving and volleying with confident authority. On one of his two match points, he netted an easy backhand volley. Then he lost his footing at deuce in that game, and jammed his right wrist as he tried to break his fall.

It was all downhill from there for Lutz, who lost that game and the next 12 in a row. He kept fiddling with his wrist, shaking it and his head in turn as frustration overcame him. He was a thoroughly dejected man -- his lank hair matted into a porcupine coiffure even in the pleasant night air -- when at 11:40 p.m. he finally lost a match he should have wrapped up routinely more than an hour earlier.

Borg -- who for the third straight year has come into the Open seeking to nail down the elusive third leg of a possible French-Wimbledon-U.S.-Australian Grand Slam -- said he was not troubled by his suspect knee, which he injured while jogging during his honeymoon last month.

Borg took five days off after defaulting to Ivan Landl in the final of the Canadian Open, then resumed workouts last Friday. He gets daily ice and heat treatments on the knee, and said after the match: "It hasn't been sore the last four days, so I kind of forget about it. It didn't bother me at all."

Neither did Aubone, ranked No. 161 in the world, who is not to be confused with his countryman Guillermo Vilas. He jerked Borg around the court, making him sprint and scramble for drop shots and sharply angled junk, but did not have the serve, volley, or consistent weight of shot to make Borg fret.

Aubone came on court carrying a six-foot racket for promotional purposes and poosed solemnly for photos with the monster weapon, but his performance peaked in that prematch playfulness.

"I think he's 100 percent. I've practiced with him the last couple of days, and he was running around fine," said Vitas Gerulaitis, last year's runner-up, who drubbed wilting Vince Van Patten, 6-3, 6-4, 6-0, in the stadium opener.

Gerulaitis has taken most of the summer off, and feels fresh to battle in the heat, which took its toll on such veterans as Stan Amith, 7-6, 6-4, 6-0 loser to Mel Purcell, and Marty Riessen, beaten by Shlomo Glickstein of Israel, 7-5, 6-1, 6-1.