My suggestion would be to look into an equine science program that offers courses on anatomy & physiology, equine psychology, things like that, and go from there. If you can't find one or aren't able to afford it right now, then see if you can get a job or intern at a rehab facility to get your feet wet and begin gaining experience.
Additionally, do what you can to read up on the topic of equine rehab. I don't know of any, but there must be at least a few books on the topic.
Idk if she's done a post on it, but Christine Meunier's site equus-blog.com covers a wide and vast array of equine careers. You might be able to find more info there, as well. And of course following some rehab places on social media will help you keep up to date on things like current practices and new advancements.