www.gloucesterrugby.co.uk "This is obviously devastating news for James and for Gloucester, particularly at this stage of the season when we are chasing play-offs and semi-finals.
"It is also likely he will miss out on a place in the World Cup and that is exceptionally bad luck for a wonderfully gifted individual who is capable of changing the face of a game.
"Everyone associated with the club wishes James the very best in his recovery and we are right behind him."
Forrester, who signed a new contract that will keep at Kingsholm until 2010 in January, suffered the injury in the first-half of Gloucester's 35-13 victory over Bristol.
He will see a specialist later this week to manage the next course of his recovery but is likely to require an operation.