Ska picked up a scent in the back garden of a house and led handler Pc Keith Bennett to the woman, who was treated by paramedics.
Police were called at around 12.40am amid fears for the woman's safety, and the Dogs Unit was called in after evidence she had been injured was found.
She is currently recovering in hospital and officers are not looking for anyone else in connection with the incident, which happened in the Northfield area of Birmingham.
Insp Russ Evans said today: "When people think of police dogs they often picture them chasing down criminals who are trying to get away from crime scenes but they actually have many other uses - as last night's incident clearly shows.
"Our dogs are highly trained and are able to follow a scent over long distances, in all sorts of conditions - so when someone is in grave danger, they really can make the difference between life and death."