Could be the peroneal tendon. It runs down the outside of the ankle and a little more than halfway along the outside of the foot where it attaches behind the 5th metatarsal. I had that pain for a while and what seems to keep it under control is a lot of one-leg balance exercises. That helps strengthen those small stabilizing muscles. I stand on one leg and hold the other leg up so the thigh is parallel to the floor, and the glutes of the standing leg contracted. I try to sway my upper body slightly in all directions to make the leg muscle work harder. Close your eyes for even more of a challenge!

I had this happen about a year ago. I have a high arch and femoral anteversion, which leads to supination and striking on the outside of my foot. I read quite a bit (one of my favorite articles was this: http://www.irunfar.com/2012/10/is-your-plantar-fasciitis-plantar-fasciitis-and-what-to-do-about-it.html.) I found that last article by searching "foot pain not plantar fasciitis." I have since switched shoes to Hokas (Stinson Trail) and love them. I can literally run 50 miles with NO foot pain. Before I was feeling every rock/aberration in the trail any time I went over 20-25 in a training run.

I am training for a 50 miler. I have had slight ongoing pain for a while but I really aggravated it when I did my back to backs on the road last weekend. The pain is on the bottom outer part of my foot. Any idea what this could be? I am icing like crazy.

I've run a lot of hard miles in the past month and have been hit by a similar sounding pain.

Some of the pain is on the top of the foot and it feels like it's in the metatarsals. My hunch is that's an issue with the tendons, similar to extensor tendonitis though I don't think it's caused by overuse due to dorsiflection.

On the bottom of the foot, I've felt the moderate pain that you're describing and I've concluded it's plantar fasciitis. Dull pain in the AM, though that becomes a sharp pain as the injury worsens, that goes away upon walking.

I've read a lot about running over that past few years (books, magazines, web sites, blogs, etc.) and this is the best piece I've seen on PF:

http://www.runningwritings.com/p/the-injury-series.html

His reporting on other maladies is excellent, as well.

I don't like not running. Not at all. But I do also realize that "running through an injury" can be an excellent way to wipe out months of hard work when/if the injury sidelines me. I don't know if your injury will escalate but I do know that, even without cross training, we lose only a small amount of our cardiovascular fitness. Jack Daniels say that we should adjust our training paces by only 2.7%, for example, after a 2 week layoff and that figure is still under 5% at the 3 week mark.