Witnesses are being sought after a crash on Wolviston Road in Billingham.
A blue Ford Fiesta was travelling southbound in the outside lane when the car lost control on the left hand bend over the railway bridge and crossed the central reservation, spinning into oncoming traffic.
The Fiesta then collided with a blue Fiat Punto travelling north, shortly before 5pm yesterday.
The 27-year-old woman driving the Punto was taken to James Cook University Hospital, in Middlesbrough, for treatment to a broken right knee and injuries to her pelvis.
Her two-year-old son, who was also travelling in the car, received treatment for bruising to his face and neck.
The 18-year-old driver of the Ford Fiesta was taken to The University Hospital of North Tees, in Stockton, for treatment to a broken collarbone.
Anyone with information is asked to contact PC Lee Benson on 101.