The Scotland midfielder has torn ankle ligaments.
The Scottish international midfielder has been integral to the club's good form this season and the energetic midfielder will be sorely missed.
Not as sore as his ankle mind. The 28-year-old confirmed he had torn ankle ligaments in the recent tie with Bournemouth and feared his season is over.
This is the tweet confirming his apparently lengthy absence:
Looks like season over for me with ankle ligaments tore. Just another challenge in my career to make sure I work hard and come back stronger— James Mcarthur (@jamesmcarthur16) February 4, 2016
McArthur has been one of Palace's best performers this season as they looked set for an assault on the European places.
Unfortunately a recent bout of injuries and being goal-shy has shattered those chances and McArthur's absence, along with the now confirmed injury to Jason Puncheon, is not going to help them in their battle to finish in the higher echelons of the Premier League table.
Palace have not won a game in the Premier League since the win against Stoke City before Christmas.