The as-yet-uncapped Forrester has worn the England shirt against the Barbarians already, but despite starring for Powergen Cup winners and Zurich Premiership regular season champions Gloucester, the athletic runner has not made the breakthrough to the full England side.
"I will try and keep my chin up and my spirits high, because this sort of thing happens in sport," a dejected Forrester told AFP.
"I still think that there is a chance I can be fit for the World Cup, but I won't really know until after the operation."
Forrester has formed part of a formidable back row at Gloucester alongside the likes of Junior Paramore, Jake Boer, Andy Hazell and Peter Buxton.
With Leicester's Lewis Moody still a potential injury doubt for the World Cup, Forrester's chance may well have come during the competition, with Richard Hill, Lawrence Dallaglio and Neil Back currently in the selection driving seat, and others such as Wasps' Joe Worsley also in the mix.