That is ridiculous! It’s the consultant who will have the say as to when your knees are ready for operation. See them! Get your knee exercises and do them, they do help, both before and with recovery.
If he needs a home now, start looking at some, though if you are not self funding, get in touch with SS as well.
Anyway, if both of you have to go into care/ recouperation, see how much more that would cost the NHS.
My OH was not diagnosed when I had surgery, though he definately had some form of dementia, and his dau came to look after him for a few days when I had my knee done. He managed the period while I was having hip done by himself. Not to be recommended is moving house 3 weeks post op!
Of course I was kept in hospital longer than patients are these days, but with ready meals, supermarket deliveries, it shouldn’t be so difficult! You don’t have to do a full house clean everyday!
Good luck, anyway.