A 62-year-old man was taken to hospital with moderate to severe head and chest injuries after being thrown two metres in a crash on Hunt Club Road near Cahill Drive.
Two cars crashed into each other just after 1:30 p.m., paramedics said.
The man had gotten out of one of the vehicles to assess the damage when a third vehicle crashed into the scene.
The man was thrown about two metres, paramedics said, adding that it was unclear if the third vehicle hit the man, or if he was hit by one of the first two after the third crashed into them.
Hunt Club's westbound lanes were closed at Cahill Drive and the eastbound lanes remained open.
The man was taken to The Ottawa Hospital's Civic campus trauma unit in moderate condition, paramedics said.
Police were investigating.