My mare has been short in her right hind for the past couple years. She always worked out of it, but wasn’t super happy to work. The vet said she was sore in the SI joint. He perscribed previcox. While that did mask the symptoms of her lameness, I wanted to find the underlying cause and not start injections. I recently discovered it was saddle fit!!! Check out this article, it helped me understand why my horse was sore in the first place. Hope this gives you ideas on which way to go next.