The Washington Capitals' three-game unbeaten streak and a 2-1 lead disappeared in the third period tonight as the Calgary Flames rallied for a 4-2 victory.

Possibly more significant than the result was a knee injury suffered by defenseman Rod Langway in the second period that figures to sideline the Washington captain for a few games. Langway, who played only briefly in the third, will be examined Thursday for what was tentatively diagnosed as a bruised right knee.

"I iced the puck and I was open and a guy (Joel Otto) hit me in the side with all his weight," Langway said. "I tried to lean on the boards to take the hit, but I got caught on the inside of the knee."

Bengt Gustafsson, who scored Washington's first goal on a power-play deflection, had limited action after a second-period accident in which he bruised his tailbone. He took an occasional shift in the third period, but never sat on the bench.

"I was tripped on the power play and I slid full speed into the boards," Gustafsson said. "I tried to play after that, but I couldn't really skate."

The night started ominously for the Capitals when goaltender Al Jensen was struck in the throat by a Bob Gould shot during the warmup. Jensen lay on the ice for some time, then went off for treatment, but returned before the session ended.

"I got dizzy and almost passed out, but five minutes later I was okay," Jensen said. "I felt good out there, but I don't feel good now."

It was nothing physical. With the score tied, 2-2, and less than three minutes left in regulation, Jensen bobbled a 35-foot shot by Steve Bozek and it caromed in off the goal post for the game-winner.

That goal spoiled a sensational performance by Jensen, who made 28 saves. In the second period, when Bob Carpenter gave the Capitals a 2-1 lead with his third goal, Jensen stopped 14 shots, including a short-handed breakaway by Richard Kromm.

There was a sudden change of momentum when Washington's Mike Gartner was penalized for hooking Lanny McDonald at the nine-minute mark. It was the only penalty of the third period and it took Calgary just 10 seconds to produce the tying goal, as Gino Cavallini deflected Gary Suter's shot from the left point.

The Capitals felt the crowd of 16,762 had influenced Fournier to make the call, since he had ignored a number of possibilities earlier in the period.

"They had a three-on-two (after a Carpenter shot caromed sharply into center ice) and I was the third man trailing," Gartner said. "I picked up McDonald and just touched him with the stick, like everybody does to me. He went down and got the call. The puck never came to him."

"It was a terrible call, because Mike had just been pulled down the same way," Murray said. "But you have to expect it in this league, I guess."

The teams seemed headed toward overtime when Jim Peplinski passed the puck out of the left-wing corner to Bozek, who flipped it off Jensen into the net. Carey Wilson provided the finishing touch with 2:03 on the clock, converting Kromm's pass from behind the net.

Reggie Lemelin, who had been relieved in the Flames' last two games, stopped 27 Washington shots. He too was shaken up, when Gustafsson deflected a drive by Larry Murphy off his mask not long after the Swede had scored.