Almost all running injuries are overuse injuries rather than acute injuries. That is, they’re caused by one or more body parts being unable over time to hold up to the repetitive stress of running, rather than a sudden, dramatic insult to the body, like a basketball player tearing her Achilles tendon or a football player destroying his ACL. The good news stemming from this fact is that almost all running injuries are short-term conditions. If you intervene early enough, you can calm the protesting body part and encourage it along the path back to cooperating when you run.
It’s often said that injuries are caused by runners trying to run too far, too fast, or both. While that’s true in one sense—you probably wouldn’t develop that strained calf or sore hamstring if you never ran—it’s a bit of a simplistic view. What’s easy for your knee to handle when it’s warm and you’re on vacation and running on a flat dirt path might be too much it’s cold and you’ve been working like crazy (probably sitting a lot) and you’re running in the dark on the edge of a slanted asphalt road. Always be mindful of the entire context in which your running occurs, both to avoid injuries and to figure out causes if one occurs.