September has a rhythm to it. The runners I coach start ramping mileage for fall half marathons, teachers and nurses come back from summer break to jobs that have them on their feet for ten hours straight, and almost like clockwork, somebody texts me the same sentence: “My heel hurts when I get out of bed — it goes away after a few steps, so it’s probably nothing, right?” I used to say “probably.” I don’t anymore. Because that little stab — the one that greets your first ten steps of the day and then politely disappears — is one…