Parker has spent more time on the treatment table than in the first-team following his £7million summer switch from Newcastle, and has made just seven Premier League starts under Alan Curbishley.
Curbishley has seen his squad decimated by injuries this season, but remains confident he has the players to cope.
He told Sky Sports News: "We're very disappointed because a lot of the injuries are the big signings we made in the summer.
"The players who have been playing have done fantastically well, it's made my squad that much stronger. If and when the injured players do return, they've got a bit to do to force their way back in.
"Scott Parker is out for at least five or six weeks. It's a different injury. It's the same knee, but it's a different injury, he's hurt his knee cap this time.
"He's gone into a tackle with Ronaldo, Ronaldo has fallen on him and all his weight has gone on his knee. It's very disappointing for everybody, Scott has worked ever so hard to get back, and he's going to have to do it again now.
"He's a resilient boy, he's been through it a little bit, and he'll come out stronger because of it. If it was similar injury, or the same injury, then I think we'd all be a bit disappointed, but it's a new injury, so we've just got to get on with it.
"I think that West Ham fans appreciate the difficult time we've had this year, and hopefully it can ease up a bit and we'll see one or two of them come back."