That isn't even remotely similar to my plot, Jim... heheh.
Actually it's the details that are different, not the plot. Plot here is injured child finds salvation through animal. There are a lot of books with this basic plot, but it's a real good one if you've got the details right.
I don't want anything that involves possible neurological problems- so no head injuries. And ridden therapy will not benefit broken arms in the way I'm looking for, not for a six year old.
Remember that neurological problems include nerve damage and spinal injuries. You're right that riding will not especially help arm muscles. Riding would also be probably contraindicated for a head injury, unless it was long term. A head injury would also not help you that much, I'm thinking.
Actually, riding does help a great deal concerning muscle.
In this situation you would begin with side-walkers to keep weak legs on the horse and the rider supported... and move towards a few minutes at a time without them... ect. Riding and giving cues to even a lesson or therapy horse is a LOT of work for young/inexperienced legs, never mind a girl who has run into moderate atrophy after an accident and HAS no muscle to start with.
Riding does involve muscles, but it's not a good exercise. The muscles would benefit a lot more from a structured PT program. But that requires that the patient is actually willing to work in a PT program.
Of course balance and self-esteem are absolutely paramount, but there are certainly other beneficial aspects to it.
For self-esteem I should have added in motivation. If you've got a patient that isn't willing to work with normal PT, horse riding can be very beneficial.
The Horse Whisperer is, again, worlds away from what I'm trying to do here.
But it's the last best seller with this plot.
The little girl is injured not on or hear a horse but in a car accident... her mother is strictly anti-horses due to the older sister (MC) being so thoroughly obsessed with them and going completely against the mother's every preconception about the way a "lady" should ask. She is in turn obsessive about it herself- constantly hounding the MC to drop the horses, occasionally sabotaging her lessons/plans, intercepting any horse involvement (even to the point of plush toys) that the younger daughter may have. When she begins to refuse therapy, the MC squirrels her away to the barn to meet the horses and eventually ride.
It's not going to be so much her injuries as it's going to be her motivation. You might want to think about whether you need to develop the injury so much as her lack of motivation. I didn't put in much details on my character's injuries, as it wasn't the injury, but the motivation that was important. It's also YA if that makes a difference.
MC had been in the process of saving to buy her favorite horse at the barn and was just about to do so when she hatched this plan... leading her to use the money to buy a vehicle to take little sister back and forth to the barn instead (she'd been biking previously at 17, just too horse-obsessed to care about a car). They are making good progress and little sister is cooperating with therapists again when mom finds out what's going on and threatens the BO with legal action. BO, while she loves the MC, panics at the thought of losing her place and kicks her out of the barn.
I like the story.