Hard-luck goaltender Al Jensen of the Washington Capitals twisted his left knee Wednesday night and, instead of celebrating his excellent effort in the Capitals' 4-2 victory at St. Louis, was hobbling on crutches yesterday.

Bob Mason will be recalled from Binghamton today, while Jensen awaits a Monday reexamination by team physician Stephen Haas. The diagnosis yesterday was a strained medial collateral ligament, with the likelihood of 10 days to two weeks of idleness.

Jensen was injured during the second period of Wednesday's game, which was his first game with the Capitals since Nov. 13. He finished the game, an outstanding effort, by making 25 saves, and had the knee iced down afterward. When it became worse during the team's flight home yesterday, he asked Haas to check it.

"There was a little bit of a collision and they hit my leg while I was down covering the puck," Jensen said. "I felt it then, but it didn't bother me the rest of the game.

"It was a little weak afterward, but I was hoping it would go away. It didn't; it got worse overnight. I don't know what to think. I had been feeling confident and feeling good.

"Right now, I just feel like going out there and hanging myself on the nearest tree. It's unbelievable."

His career would make an interesting television drama, except that it would be panned as too farfetched.

In two years as a Detroit farmhand, he was given short shrift by the Wings. He played only one game for Detroit, a 7-3 loss in Montreal. When the Wings dealt him to Washington for Mark Lofthouse in July 1981, there was wonder why the Capitals bothered. They already had seven goalies under contract -- Mike Palmateer, Wayne Stephenson, Dave Parro, Rollie Boutin, Gary Inness, Bart Hunter and Neal Girard.

Jensen climbed that formidable ladder to become No. 1. Last season, after a remarkable start in which he posted a 23-13-2 record and 2.95 goals-against mark by mid-January, he was voted the starting goalie for the Prince of Wales Conference in the NHL All-Star Game.

He never got to enjoy that honor. Instead, lifting weights on an offday, he injured his back and was idle for eight weeks. Nevertheless, he finished third in the NHL with a goals-against figure of 2.91.

His left knee first achieved prominence when he suffered a strained tendon in an exhibition at Minnesota Oct. 2. As with Wednesday's injury, he did not realize the extent of the damage until the next day.

He came back two weeks later to beat Los Angeles, then was ordered to rest the knee and did not play again until Nov. 3.

Finally healthy, he defeated New Jersey, lost to the New York Rangers and tied Minnesota.

He seemed to be returning to his previous form when he pulled a muscle underneath his left arm in practice Nov. 18.

Unable to play for more than a month because of resulting problems in his back and side, he in desperation sought out a chiropractor, who cured him.

Jensen played three games with Binghamton, then returned and pronounced himself ready to play. He proved in St. Louis that he was ready, but now once again he must sit and wait.

Mason, who won his last six games with the Capitals, shared the NHL's rookie of the month award for December, an honor that was announced the day after he was sent to Binghamton to make way for Jensen's return.

The Capitals, who have lost only one of their last 13 road games, will return to action Saturday afternoon at New Jersey.