2. Your Past
There's logic behind jokes about old football injuries and other past trauma to the body. A childhood fall, a broken bone that wasn't reset properly, a car accident, even how you came out of the womb can permanently alter how you carry yourself. Any subtle but seemingly locked-in change in your posture can introduce inefficiencies to your running form that can increase your risk of developing repetitive-strain injuries.
More obviously, if you lived a typical sedentary Western lifestyle for many years before you started running, the body you bring to running could increase your injury risk. Excess weight places tremendous strain on joints, tendons, and ligaments. Inactivity reduces muscular strength and efficiency.
What To Do About It: As with your inherited physical traits, take as complete an inventory as possible of past insults to your body. Look at photos for patterns of holding one shoulder higher, or one hip lower. When you've identified imbalances from past trauma, work to correct them with targeted strengthening. If you're carrying excess weight, take a long-term approach to getting to a good running weight that will lower your impact forces.