The Muirfield Riding Therapy charity at North Berwick, East Lothian, provides hippotherapy - derived from the Greek word hippos meaning horse - free of charge for people with a wide range disabilities such as cerebral palsy or multiple sclerosis.
The movement of the pony helps the riders to develop strength in weak muscles.
The charity is able to offer the free service thanks to the dedication of an army of volunteers aged from 10 to 80. Their work is supported by fundraising efforts.
Susan Law, chairman of the charity, said the ponies help "train" the muscles in people who have disabilities while interaction with the animals can also help people with learning or behavioural problems.
People are referred by teaching or medical professionals and about 100 people a week are helped during six sessions a week at the stables.
Raiden is the youngest of the 12 ponies, at seven years old, and he is being trained to take over from the oldest pony, Kishmul, 26, who is approaching retirement.
Ms Law said: "The job they do is an important one.
"During the weekly riding sessions they help provide riding therapy for adults and children who have a wide range of disabilities including cerebral palsy, spina bifida, multiple sclerosis and learning or behavioural problems. Classes are run by a physiotherapist who does hippotherapy.
"This is a specialist part of our work where Kishmul and soon Raiden, will be used for back-riding. This involves the therapist sitting on the pony working with the child in front of her.
"The ponies are trained to listen very carefully to the handlers and respond with precise movements.
"It is this movement which can bring about changes in the rider's position and responses in their muscles, teaching normal movement patterns, freeing up stiff muscles; bringing down tone, where there is stiffness, or raising tone - where muscles are flaccid. It is all done in a very controlled way.
"So the ponies used are under pressure to behave impeccably. A gallop along the beach is a marvellous way for them to unwind.
"We draw on the experience of our volunteers, some are horsey people and others might have a background in education. There's a very wide range of experience."
The centre is also raising funds for another pony to join the team after the death of 22-year-old Sonic - who had a mane like the computer game hedgehog - died last year.