Marcus Johansson got the puck between the circles, but instead of shooting, he quickly fed Knuble right in front of goalie Corey Crawford. Knuble deftly shifted the puck from left to right and flicked a shot past Crawford.
"Real heads-up play by Marcus," Knuble said. "It would have been very easy for him to bury his head to try and jam it through, but I kind of laid my stick to the side, and he put it on the tape."
The Blackhawks forced OT when Jonathan Toews stuffed the puck into the right corner on a power play with 38.5 seconds left in the third period.
Chicago got the power play when Johansson was called for hooking with 1:50 left. Coach Joel Quenneville quickly pulled Crawford to give the Blackhawks a two-man advantage.
The Capitals then dominated play in OT. Ovechkin was all over the ice for a long stretch, and Washington outshot the Blackhawks 6-0.
The Capitals moved to one point behind Philadelphia for the top spot in the Eastern Conference, and their Southeast Division lead over Tampa Bay increased to five points. The Capitals have 90 points and are trying for a fourth straight division title. They have 12 games left; the Lightning have 13.
The Blackhawks have dropped three straight after winning eight in a row.
Washington coach Bruce Boudreau is happy because all four of his lines are playing well. He said that was a big reason for the winning streak.
"All four lines were going; that's why I didn't shorten the bench," Boudreau said. "They're all contributing. It's a nice thing to see, but that's why you win -- when everyone contributes."
Ovechkin didn't score a point, but the Capitals still did fine.
Eight of the nine players who registered points were forwards, and the Capitals had an advantage in size, an edge they often have over other teams.
"I think our forwards are as big as anybody's in the league and, on top of that, they can skate," Laich said. "As a defenseman, you don't like going back for the puck ... (and) guys keep coming at you. It wears on you eventually, through a game."
The Capitals' winning streak is their longest since they set a franchise record with 14 straight victories from Jan. 13-Feb. 7 last year.
The victory was Washington's 40th, setting a club record with a fourth straight 40-win season.
Defense and timely goals have been key to Washington's streak. The Capitals have allowed just 12 goals during the eight games.
He's given up only four goals in 11 periods since replacing Neuvirth and made 27 stops against the Blackhawks.
This was the only meeting between the two teams this season.
Chicago controlled play early. The Blackhawks got the game's first five shots, kept the puck in the Washington zone for long stretches and took a 1-0 lead on Nick Leddy's goal at 4:46 of the first period.
The Capitals tied it 1:25 later on Gordon's short-handed goal. Washington got a break when the puck eluded Patrick Sharp near the left point, bounced off the boards and right to Gordon, who took off on a breakaway and beat Crawford with a long slap shot.
"It bites pretty hard when you get scored on short-handed," Toews said.
The Capitals took a 2-1 lead on Arnott's power play goal with 53.7 seconds left in the period.
Tomas Kopecky tied it early in the second period. Kopecky fired a shot at the goal from the left corner that somehow slid through Holtby's legs, apparently bouncing off his back skate and in at 3:09.
Laich gave the Capitals a 3-2 lead when he scored at 6:23 of the third period.
The Capitals finished with a 42-30 advantage in shots and often controlled play.
"We'll take the point," Quenneville said. "We weren't very good today. We were very generous in all the goals that we gave them and could've done a better job defending in those situations."
Gordon went 27 games without a goal; he's now scored twice in five games. ... The Capitals are the first team in NHL history to get seven or more victories from three goalies age 22 or younger. ... Marian Hossa's eight-game point streak ended in Chicago's last game, but he started a new one with an assist. ... Leddy's goal was his first since Feb. 1.