I was doing my daily run and somehow without knowing how I clipped my foot and it threw off my stride. I fell forward. I put out my right arm to break the fall and it ended up torquing my body backward to the right while driving my elbow up into my chest. I ended up- for that moment- with a large road rash on my leg, bloody and a sprained wrist. But I also found that I was having some problems with breathing- it hurt. And two days later my right knee blew up to the size of a basketball.
In the end, here is the score- sprained wrist, road rash, 2 broken ribs, and a torn right medial meniscus with damage as well to the medial synovial plica, both of which had to be corrected or removed via arthroscopic surgery (the surgeon was Dr. Payne, for real...) . Was off my feet for 2 weeks, came back to run and found that the absence of so much knee tissue affected my ability to handle impact forces and took up bicycling, which is what I now do to this day.