He still isn't what you would call "comfortable". He looks imploringly at us, but we don't understand what he is trying to tell us. He doesn't seek out our attention-- he mostly seeks comfortable repose inside and out. We plan to take him for a vet exam this week to make sure that he is not hurting. His knee should be fine now, and we can't quite put our finger on what it is that seems uncomfortable about him, but we want to be sure we aren't missing anything.
And we have caught him actually engaging the puppies in play on more than one occasion recently. And he was playing with Ben lately too! So it could just be that he is taking his time, taking it all in, and on his way out of his shell...