Ovechkin, representing Russia, sustained the injury in a collision during a game against Germany at Minsk Arena in Belarus.
Ovechkin went to a hospital for treatment after a hit to the knee from German forward Marcus Kink midway through the third period. Ovechkin stayed on the ice for several minutes before getting helped off the ice.
Kink was not penalized on the play.
The International Ice Hockey Federation said Ovechkin will miss Russia's final group game against host Belarus on Tuesday but is still with the team.
Russia's ice hockey federation said it is not clear if Ovechkin will be able to continue playing at the tournament. Ovechkin wrote "all's OK" on Twitter with a photo of him giving a thumbs up.
Ovechkin led the NHL with 51 goals this season, although the Capitals failed to make the playoffs for the first time since 2007, forcing the franchise to fire head coach Adam Oates and general manager George McPhee.