A better way to go is to first mention the internal connection between pain and having a body. For although pain without behavior sounds like something that makes perfect sense, pain without a body is a puzzling idea. The connection looks internal. The idea is that thinking about being embodied cannot be completely severed from the forms which this embodiment takes—pain being one of them, movement being another, behavior being yet another.
At bottom, pain is the form (in the Aristotelian sense) of certain types of behavior (and not, for instance, the form of a certain kind of movement), and to explain the Wittgensteinian view requires making forms visible, or, what comes to the same thing, showing, getting people to see, the symbols in the sings.