Financial terms of the deal were not disclosed but local media reported it was worth $2 million for the 2011-12 season.
The 38-year-old Knuble had 40 points with 24 goals in 79 regular season games, becoming the eighth active NHL player to score at least 20 goals in eight consecutive seasons.
He was one of Washington's key players in the closing weeks of the regular season, scoring nine goals and four assists in his final 14 games.
The Eastern Conference leaders begin round one of the Stanley Cup playoffs against the New York Rangers on Wednesday.
(Reporting by Gene Cherry in Salvo, North Carolina; Editing by Frank Pingue)