The goalkicking back has also been ruled out of his club's opening two fixtures in this season's Heineken Cup, with the Ospreys not keen to rush him back too early.
"Gavin is making great progress," stated Ospreys manager Derwyn Jones. "The operation was a success, and he is now pain free. He hasn't played for a while, so he will be going through an intensive conditioning period before we welcome him back onto the pitch with the Ospreys."
Henson joins Gethin Jenkins on the injury list for Wales, while winger Shane Williams is a doubt for the autumn fixtures due to a groin problem.