The defenseman is expected to need 4-6 months to recover.
Kempny has not played since sustaining a lower-body injury against the Tampa Bay Lightning on March 20.
In 71 games this season Kempny had 25 points (six goals, 19 assists) and a plus-24 rating. He averaged 19:11 of ice time per game and played with John Carlson on the top defense pair at 5-on-5.
"I think I'm a little bit more aggressive at the (blue) line and keeping guys out of the zone, and in-zone he's a little more aggressive in terms of down below the goal line and stuff like that," Carlson said March 22. "I think we obviously know each other's games and work off each other pretty well. He's a big piece of this team and we're going to have to all step up."
Recently-acquired defenseman Nick Jensen is someone who could take on a bigger role in Kempny's absence. Jensen averaged an NHL career-high 20:48 of ice time in 60 games with the Detroit Red Wings this season before being traded to the Capitals with a fifth-round pick in the 2019 NHL Draft on Feb. 22 for defenseman Madison Bowey and a second-round pick in the 2020 NHL Draft. In 18 games with Washington, Jensen is averaging 16:39 of ice time and has five assists.
"He's a guy that you could expect to see getting some more ice time here without Kempny being in and some different situations as he grows, different opportunities," Capitals coach Todd Reirden said of Jensen. "You might see him occasionally with different partners … as we try to find the right combo that works for us."
Acquired in a trade with the Chicago Blackhawks on Feb. 19, 2018, Kempny had five points (two goals, three assists) in 24 postseason games to help the Capitals win the Stanley Cup last season.
Washington, which is first in the Metropolitan Division, plays the Montreal Canadiens at Capital One Arena on Thursday (7 p.m. ET; NBCSN, NBCSWA, TSN2, RDS, NHL.TV).
