The only thing we living creatures share is suffering. Just as Jesus suffered and in that way, we are like God.
I also think the knee group didn't mean anything, if only because I've been that drunk and done it to friends, then made a gross joke after. Really, I just think John is Drunk Trash, and there's SO MUCH BETTER to use in a discussion as evidence. If it was meaningful, it's something I'd consider the least indicative. John nodding off on the couch then slapping Sherlock is more drunk husband-y to me. Or maybe the entire scene as a whole, but not the individual knee grope moment,