externalism in experience/sensations

ok this is going to be really short and i hope to expand on this later, but i was thinking about externalism in sensations. here's my thought: when you feel a pain, where exactly do you feel it? many people have argued that you can only feel pain in your brain. that is, if something pinches you on the hand, you feel the pain in your brain nevertheless because that's where the c-fibers directed.

but, if you realize that each particular pain has an origin, then that origin is necessary and thus, even though the brain registers the pain, it is actually felt whereever it was actually felt.

this intuition is largely caught in a thought experiment that to my knowledge, is new. it is no doubt inspired in part by kripkenstein on other minds and mcginn on imagination, but here goes.

is it possible to imagine a pain in your knee? well, sure, you can imagine your knee being in pain, and in the simulated pain, it is your knee that has the sensation. however, can you imagine a pain in your knee in your elbow? well that doesn't really make sense. you could imagine a pain in your elbow, even a particular type of pain, the same your knee had, on your elbow (sharp vs. chronic, etc), but you can't imagine a pain in your knee in your elbow.

if i'm right about this, then particular pains have necessary origins, which lend support to an externalist account of sensation.

however, an objection quickly arises in the cases of pain in phantom limbs. i either have to come up with a pretty damn good explanation for them, or categorize them as non-legitimate pains. i tend to agree with the latter, but then i'd have o come to the conclusion that sensations of pain are not the same as pain. however, kripke himself has argued for this claim, that sensations of pain ARE pain (and the argument seems to be sound).

how to reconcile my seemingly correct previous intuition with kripke's? this'll take some time to figure out.