The club wished Elanga, who has been at Man U on junior and senior level combined for eight years, a "speedy rehabilitation" at X but gave no further information about the type of injury the 23-year-old suffered.
Elanga - who was bought from Nottingham this summer - has made 17 league appearances for Newcastle this season and is also an important part of the Swedish national team that plays in the World Cup play-off against Ukraine on March 26.
Newcastle lost the away match against United 0 - 1. Patrick Dorgu scored the winning goal in the 24th minute.
