I don't know, Ramona basically said that was a specifically sexual kink of Roxy's. Granted the back of the knee is somewhat more innocuous than most places, but I still found it a bit, irk... traditionally intimate doesn't mean anything to the individual. I mean, with Envy (or, as I originally thought, with Ramona and Roxy) it just feels better because that's their shared history in play. Whereas slicing in half isn't really more violent than exploding the skater guy.