But the La Galaxy striker should be fit in time for Ireland's Euro 2016 opener againt Sweden on June 13th if required.
Keane failed to make an appearance in Ireland's two recent internationals against Switzerland and Slovakia due to the injury.
But he looks certain to make Martin O'Neill's 23-man squad for this Summer's tournament in France.
The news comes a day after Jonathan Walters confirmed he too had a knee operation and hopes to be back in action in less than three weeks.
