That'll larn him!
Seriously, though, I'm sorry you're having a "down" day. Don't try to stop it, because tears are healing, too.
I'm glad you realised that unstable emotions and the blues are a part of this recovery - and you know that they will come to an end, as you continue to heal.
It's quite right that, with two new knees in a relatively short while, you have been hit with a double whammy. Both your body and your mind have had a lot to deal with.
Keep on resting and pampering yourself. Sometimes tact isn't a husband's strong suit.
We're here to listen, if you want to vent, or need a shoulder to cry on. We understand, because we've been there.