What is the ruling on a woman working as a physical therapist and treating men and women?

It is permissible for a female doctor to examine and touch a woman's body that is not 'awrah (parts that must be covered), and it is permissible to do so for the 'awrah when there is a need. As for her examining and touching a man's body, it is not permissible except in cases of necessity when a male doctor is unavailable, based on the hadith of Rubayyi' bint Mu'awwidh. This is permissible for an old woman (al-mutajalliyah) from whom no fitnah (temptation) is feared.