Ways to keep a dog mentally stimulated after an op?

Hi all

I've just taken Molly to see a bone specialist who has said that her luxating patella is quite bad and needs immediate medical attention. The upshot of this is that she is booked in for an operation on the 21st of October. However, the operation is quite a big one and I've been told that she is going to be unable to go for walks or do anything strenuous for around 8 weeks after the op.

My plan is to try and keep her in her crate as much as possible during this time but my question is, what can I do to keep her occupied and get her brain working while she's out of action? Normally I'd just give her a Kong to keep her occupied but obviously with her not getting much exercise I don't want her putting on lots of weight while she's out of action. I'm not sure if doing lots of our usual training will be any good either as she gets very excited when we do that and I want to keep her as calm as possible.

I've looked into maybe booking some hydrotherapy sessions for her but what else is there I can do with her while she's recovering?