Disability for a (kind of) pre-existing injury?

In my childhood/high school years I played a lot of sports and was pretty prone to ankle injuries. Stepping in holes, or cutting too hard on some turf would make my ankle turn over. I was never seen by a physician for it, and it always just healed on its own. About 6-7 months ago, I ended up hurting it again on a mission, and it hasn’t been the same since. I’m currently in physical therapy, and there’s talk of surgery. I had no problems in basic training, AIT, or any part of my short career up until a few months ago at one specific point. Now it’s preventing me from doing PT to my fullest extent, and makes it extremely difficult and painful to participate in the ACFT. My concern is that all of the MD’s I’m seeing for it (Physical Therapist, and PMC) are sort of hinting that it’s a pre-existing injury. That worries me, that in the case I have to get out of the Army because of it, I’m afraid that they’ll rule that they don’t owe me any disability because they all think I came in with this injury, even though it’s never been as bad/a permanent issue until hurting it on a mission. What can I do in the case I do have to get out?

Note: I haven’t screwed myself by telling them about pre existing injury. It’s apparent through physical evaluation that there’s permanent damage. Which I do believe is true, but it’s never been a chronic issue, not until now. Thanks in advance for all the help.