Farmer's daughter Sarah Beal was riding with the Derwent Hunt at her home, Abbey Farm, at Yedingham, near Scarborough, when she was seriously injured.
She was riding a large Hunter, 15 to 16 hands high, when the accident happened in front of her mot
her, Helen, on Tuesday lunchtime.
Eye-witnesses said the horse reared, fell backwards, and landed on top of the teenager, knocking her out.
Paramedics were called to give her first aid at the scene, and fellow hunt members said she was unconscious for at least five minutes.
She was airlifted to York District Hospital, where she was operated on for serious chest injuries.
Her condition was yesterday described as "poorly", in intensive care, and her family said she had suffered serious internal injuries.
Mum Helen said: "Sarah loves riding and we were out hunting at the farm next to the house.
"The horse reared, threw Sarah to the ground, and landed on top of her. It happened so quickly there was nothing she could have done to stop it happening."
A member of the family, who asked not to be named, said they did not want to talk further about the accident until more was known about Sarah's condition.
"We do not really know," he added. "They're doing another scan. She is still under sedation. She was only really conscious before the operation. She has a ruptured liver and pancreas."
The teenager recently started work in the managing director's office at the Yorkshire Post's sister paper, the Scarborough Evening News.
Sarah Morley, secretary of the Snainton-based Derwent Hunt, was riding with her when the horse reared.
"It was a freak accident," she said. "The horse just reared up and rolled on her. She had been riding with the hunt since she was tiny. She competes all over and is a very good rider.
"This was one of those things which could happen to anybody. We are all thinking of her and wish her well. We just want Sarah back. Everyone is worried about her and is hoping she gets better soon. She's a lovely girl and we all like her very, very much."
She said that although Sarah was riding a large horse, she was an accomplished horsewoman who regularly took part in the hunt and had been riding since she was ten. "Despite her young age she was an experienced rider. Everyone is just so shocked."
She added: "The ambulance crew were excellent. They arrived very quickly and called the air ambulance. She was airlifted out of the field. I think she was unconscious for about five minutes."
The Derwent Hunt, which traces its history to 1808, has 40 fully paid-up members and 70 hounds. It meets on Tuesdays and Saturdays, on land north of the A170 and south of Scarborough and Pickering.
mark.branagan@ypn.co.uk
