The injured leg of the horse was amputated in an emergency surgery that took place on late Thursday night.
The horse's amputation surgery took place two days after his fractures were fixed by external fixation by a group of 10 doctors - six from Pantnagar and four district veterinary officers.
Joshi's arrest comes after the Police arrested BJP worker Pramod Bora from Haldwani for forcefully pulling the bridle of the horse and causing its fall during the protest.
The incident took place on March 14 during a protest march against Uttarakhand Chief Minister Harish Rawat for "misuse" of funds. The horse, Shaktiman, who was a part of Uttrakhan Mounter Police, fell down during the protest after Bora allegedly tried to pull him down.