Vunipola has been ruled out for 16 weeks with the cartilage damage sustained in Saracens' 41-13 Aviva Premiership victory over Sale at Allianz Park on Saturday and will miss England's autumn series against Argentina, Australia and Samoa.
"For any team to lose a player of the ability of Billy is a blow and he will be missed through the autumn for both Saracens and England," Saracens director of rugby Mark McCall said.