When you overpronate, your feet turn in too much at impact, which leads to all sorts of problems like knee pain, foot pain, shin splints, plantar fasciitis, Achilles tendonitis—the list goes on. You may also notice that if you pronate badly enough to cause injury (or even pain), you don’t experience it in both feet; usually, one is worse than another. Typically your right foot will be more affected than your left (since most people are right-handed).