An air ambulance was sent to Doe Bank in Great Barr along with police, paramedics and firefighters after the woman and her dog were hit by a car at about 5pm on Wednesday.
An off-duty nurse treated the woman before she was taken to the Queen Elizabeth Hospital in Birmingham.
Police said the woman has a broken leg and her pet dog died, while a number of people fled from the scene.
Photos from the scene showed major front-end damage to the car involved in the crash.
A spokeswoman for West Midlands Police said: "We’re investigating after a pedestrian was hit by a blue Renault Clio on Doe Bank Lane, Great Barr just before 5pm yesterday evening.
"The elderly pedestrian was taken to hospital for treatment, where a scan revealed she’d sustained a broken leg.
"Sadly her pet dog was killed as a result of the collision.
"A number of people fled the scene, who we’re currently trying to trace."
A West Midlands Ambulance Service spokeswoman said: “An off-duty nurse was on scene administering first aid to the pedestrian, a woman, who had been involved in a collision with a car.
"The woman suffered serious injuries and, once treated and stabilised on scene by ambulance staff, she was taken by land ambulance on blue lights to Queen Elizabeth Hospital Birmingham for further trauma treatment.”
Anyone with information is asked to contact police.