Patients and staff inside the clinic helped the woman and restrained the man at View Street Medical in North Perth just before 9am.
The woman, aged in her 40s, was taken to Royal Perth Hospital with serious injuries.
"A man aged in his 50s was taken into custody and is now assisting with inquiries," Western Australia Police said.
He is yet to be charged.
The medical centre has closed for the remainder of the day.
