There is a suggestion it may be ligament damage and it seems he will be out for at least 2 weeks.
He will definately miss the trip to Milton Keynes on Saturday and the visist of WBA next Tuesday. The home game against Ipswich in 8 days time is probably too soon as well. That means the soonest we could expect to see him back is the trip to Stoke on Dec 6th.
More updates on Kav when they are available over the next week or two.