Good Morning and welcome! I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
AS you know, this is a very stressful work for horses and they will need to be in excellent physical condition in order to compete in such a difficult sport. The prognosis will depend on the position of the Polyarthritis and the extent of it in such a young eventer. In general, however, even the beginnings of Polyarthritis will impeed Chocolate Chips performance so he may not have a good prognosis for this sport that is so demanding. It is best to treat with anti inflammatory medications as well as Glucosamine and then xray again after 2-3 months and this will give you a better feel.
Does that make sense to you?
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