I have found the ChiRunning (http://www.chirunning.com/) people do a good job of describing the physiological issues and this short video is a good visual guide.
As you increase your step count 'per day' and 'per week' above what your body is used to, the mechanics of taking steps needs to addressed - and I had not done a very good job of it before this point.
A very small adjustment to the insert in my left shoe was needed, literally about 4mm, after which I felt great. The following week (let's call this week 2) I even set a new personal running record at 6.9 miles on Saturday. Later that day I also went for a 4 mile walk with my kids followed by a 7.8 mile solo run on Sunday. At 27 running miles for the week it was a big jump up in mileage but it felt great and I decided to start training for a full marathon!
The following Saturday (week 3) I met up with the West Coast Road Runners who were training for a full marathon and ran (survived) 10 miles with them. It felt good to have accomplished that distance for the first time ever, although my body was pretty numb. The next morning I did five miles to recover and that week 'only' completed 26 miles due to a business trip.
Saturday of week four my personal goal for the day was 11 miles even though the running group was heading for 13. The first half I felt great and was able to focus on preserving energy while learning about how to hydrate and refuel while running so I decided to for the 13. Progressively through the miles I had right ankle pain that became so bad that I had to stop running and mostly walked back to the car.
I made a big - strategic - classic - new guy mistake and broke a fundamental training rule even though I was vaguely aware of it! "Do not increase mileage by more than 10% in a week"!
My mileage increases were:
Week 1: 66%
Week 2: 55%
Week 3: 30%
Week 4: 17%
That's when I became aware of the statistic that 70 - 80% of running injuries occur at or below the knee. For me so far it has been 100%! Stay tuned to find out what happens next.