Shin splints and stress fractures are, unfortunately, a part of life in the Army. Apparently they are one of the largest causes of being put on profile. In my case, I got a pretty bad shin splint after my first 10k ruck march on the hills of Fort Knox; they are, after all, named Misery, Agony, and Heartbreak for a reason. That healed up alright, did a bunch of rucks and ruck runs last fall, but then this January when I ran my 2-miler I ended up with shin splints again for no real reason. I did a 6-mile ruck two days later and then again a week after that. Realized my shin was hurting far more than it should have, got some shooting pains all up and down my leg every time I ran or jumped (damn those side-straddle hops), and made an appointment to visit an orthopedist. One x-ray and one 2-hour MRI later, and I was diagnosed with a mild stress fracture. I'm currently going to physical therapy for it and it feels a lot better, but I'm still on a no-running profile, and I had to put it in my packet for LDAC.
The lesson here is, always stretch properly, don't ruck on shin splints, and for goodness sakes don't push yourself to the breaking point. As long as I follow my therapist's advice, I'll be fine for LDAC, but I had to forgo the Bataan memorial death march and the German Army proficiency badge. Both of which I can do next year, of course, but I'll have to start from scratch on the training.
