Vampire takes bashing (Not the question ;-)

Shooting someone in the head upgrades it to Aggravated.

The question:
If someone targets the knee of a vampire taking the -5 mod on the roll could you then argue that the damage should be aggravated due to the possibility of ripping the join apart?

I would have said no. The reason it's aggravated when you shoot them in the head is for mythical/supernatural reasons, the brain still being required for the Kindred to function, and the sheer complexity of the brain making it hard as hell to recover from. The knee, on the other hand, is like any other joint, and isn't mystically more complicated to repair than any other injury.

Thanks - I can accept that explanation :-)