There was a good one-page how-to in a recent Triathlete magazine on running stride. Those things always are lame, in my opinion, but this one supported my current mindset, so I liked it. Among other things:
1. Mid- and fore-foot running works for some but not necessarily for everybody.
2. The great Haile Gebreselassie (even in a world with Mutai and Kipsang, still the best distance runner in history) apparently taught himself a longer forward reach when moving to marathon.
3. Recommendation: if you have run for years injury free, maybe you are actually doing it right.
This is consistent with my observation when watching video from the Craig Alexander's first (of three) win at Ironman Kona that Alexander, one of the top very few best ever runners in Ironman triathlon, has a very slight heel strike.
And it is consistent with my experience that I felt fine and ran fine until I made a concerted effort to run differently, starting about 12-18 months ago.
Today I ran for the first time in a couple of weeks. I made a concerted effort to run the way I grew up running. Heel first, but not obnoxiously so. I feel the knee as I stand here, but it is not yet terrible. Knocking on wood . . .