This is a good forum because of all the folks that might have similar questions and experiences.
In this case, perhaps only a tiny minority of people share this experience, most other view the thread as noise.
Although I'm sorry that others share this experience, I'm also glad I'm not alone.
2008 and 2009 were the worst years for me for this pain, and after seeing many doctors and therapists, in 2010, I figured that it might have to do with the extra cycling, as I started commuting 150 miles a week year round in 2007.
In fact, looking back, I had similar, but very minor and temporary, leg pain going back more than 10 years before full time commuting on the first downhill hikes of the season
It could have to do with age, lack of cross training, and/or other factors.
Soon, I start another long distance walk (140 miles, 18,000' up and down), so that will give me another data point.