"My head hurts" translates as "me duele la cabeza" and not "mi cabeza duele." I was taught that possessive pronouns are redundant and hence dropped when speaking of body parts. Does this rule apply to any other possession or is it strictly on for body parts? If so, why? Also, how would one translate the same sentence if the subject is someone else? Let's say the sentence is "His leg hurts". Would it be "Le duele la pierna"? Or would it be "Se duele la pierna"? To make things even more complicated, what if a name is given, e.g., "Ronaldo's leg hurts"? Without Ronaldo, I would assume leg (or whatever body part is in question) would be the subject. But with the name specified, there seem to be two subjects...that's so unnatural to English ears!
His leg hurts would be correctly translated as "Le duele la pierna", literally, "The leg hurts him". In this respect, it functions exactly as in English, except that an object is obligatory, rather than optional. If you wanted to say that Ronaldo's leg hurts, you would just specify him as the explicity indirect object: "Le duele la pierna a Ronaldo".
In Spanish, when possessed things affect their owners, the ownership is very commonly shown via the indirect object. This isn't exclusive to body parts: "Se me averió el coche" will be most commonly be interpreted as "My car broke down on me".
Possessive pronouns can be used in these structures, but normally only when the thing being owned is affecting someone else, quite uncommon with body parts such that at the moment, I can't think of any example that's not overly contrived. But notice in the previous example, if I were driving your car, I would say "Se me averió tu coche".