Here's my take, and reply:
25 years of 'research' (collected wisdom, really) based upon coaching runners, endurance athletes, and athletes in run-based sports has taught me a few things about injuries.
Firstly, there are two types: (1) acute, such as a joint sprain, a jar, or a contusion; (2) chronic, overload and recurring (related injuries) which normally come on over time...getting slowly worse and often ignored by a runner.
The causes of these are always an individual mix of three main factors (a) mechanics: normal structural or functional alignment which is either inherent (the way you're born and built) or external (eg. shoes, camber, surface), (b) loading: what, how much, how fast and where (eg, hills) they run, and (c) time.
Most runners get injured simply because they do too much (fast) running to soon, or make (relative) sudden changes to their running/training load.
Central cardiovascular fitness can improve over a few days. Muscle function improves over a week or so. Yet tendons, joint structures and bones can require weeks and months to adapt to new loads (dependent upon mechanics, and training and injury history).
It comes as no surprise that the most common run injuries are Achilles, hamstring, gluteal and ITB tendon related or foot, shin, knee and hip joint/bone related. Secondary injuries are common too because an initial injury was neither rehabbed properly, it's causes weren't eliminated, or the runner progressed back towards 'normal' training to soon.
Magazine and on-line articles that promote "must do", "need to do", and "should do" sessions - which are often watered down sessions from elite or competitive athletes do not help the mindset of beginning and mass-participation runners in regard to "load" or "change in load" (too much of 'x' to soon) :-)
