The former England midfielder, 27, has been forced him to return from a season-long loan at West Ham for treatment at Tottenham with the injury he picked up in training last week. He underwent surgery on his left knee on Wednesday.
Hammers boss Sam Allardyce said: 'It is a great shame for David as he had settled in well to the squad. We wish him well and hope he has a speedy recovery.'
Short stay: David Bentley (left) made five appearances for West Ham
Rare sight: Bentley in action for Spurs
Bentley had been hoping for a spell of first-team football after falling out of favour at Spurs under Harry Redknapp since his ?15million move to White Hart Lane in 2008.
The ex-Blackburn star also spent an unhappy spell on loan at Birmingham last season, making 13 appearances as Blues were relegated from the Barclays Premier League.
The winger had made five appearances at West Ham so far this season but exploratory keyhole surgery on Tuesday revealed a problem and he returned to Spurs.
And now Bentley has had his worst fears confirmed by being ruled out until around April, leaving him fighting to play again this season.
Matt Taylor, meanwhile, is back in training with the Hammers after missing the last club's two games and is in contention to face Blackpool at Upton Park on Saturday.
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