My arm has fallen?" translates to a human in a standing or seated position, with their arm hanging limply at their side, appearing to have fallen due to a lack of movement or muscle control. Perhaps they look surprised or bemused, examining their own arm as if it's behaving unexpectedly.

A person, either standing or seated, has their arm hanging lifelessly by their side, indicating a lack of movement or muscle control. Their facial expression suggests surprise or confusion as they examine their own arm, as though it's behaving in an unexpected manner.