Muddy calves and running style

I did me a bit of a 10k at the weekend, mixed terrain so a bit muddy, but I was a bit confused after I finished when I noticed a neat line of mud up the inside of each leg up to just below the top of my calf.  I didn't fall, it wasn't particularly splashy mud and everyone else looked a lot cleaner, so I struggled to work out where it came from. 

Having looked at the pictures afterwards I think it must be the way I'm running, my toes seem to be pointing outwards more than other peoples seem to be and I'm guessing the back of my heel must be occasionally hitting the opposite calf, not enough for me to notice but enough to spread a bit of mud about.

Anyone have any thoughts on this? If this is due to the way I'm running, is it something I ought to correct, if its likely to be making me more prone to injury or slowing me down? Or is it something aesthetic I can just ignore?

Perhaps the others jumped over or navigated around the puddles?  I can't see an issue here.

If you're concerned about injury wrt the positioning of your feet, do plenty of calf stretches with your rear foot facing forward, or as forward as you can.

Possibly weak glute muscles;

http://runningtimes.com/Article.aspx?ArticleID=23920

Thanks for the link, I'll look into that. I'd be surprised if it was glutes, they get plenty of regular exercise at the gym, but maybe I need to try some different exercises.  The pictures in that article definitely looked like they'd kicked their other leg too, mine looked more like a vertical scrape.

As for puddles, it wasn't puddle-y mud, more sticky mud.  I'm not concerned about injury as such, more just curious.  I can find plenty of stuff about foot position with regards to where you strike or pronation, but not much about the actual angle between the direction you're running and the direction your feet point when they hit the ground.

Its probably nothing worth worrying about, just made me a bit curious.