He suffered a cartilage njury just a few days after completing his move to Burnley and will have surgery next week. It is thought he will be out until early 2012.
Manager Eddie Howe said: "It's a serious one. Danny is going to have an operation next week but we are looking at four or five months and it's a real blow for us.
"He did it on Thursday in shooting practice There was nobody else involved and he just landed on his shooting foot and felt something go in his knee.
"He's never had a knee problem before and sometimes you try and work out a reason for these things. We've been scratching our head, but it's just fate really and that happens.
"We just have to make sure we get Danny back. We bought him for the future and he's still only 19. He will come back from this, but it's a blow to lose him just as he is settling into the club."
Howe confirmed that we would be looking to bring in a striker on loan.