Not sure what this is from. Usually the pain radiates up my leg, but since I've been going with incline rather than speed on my treadmill, I only feel the pain right at the crease where my foot meets my leg on the front. I get the same pain when I walk outside, so it's not the treadmill.

Any ideas?

Sounds to me like one of the many variations of shin splints! Here is a stretch that works wonders for me and (for friends that I have recommended it to). I learned it years ago in aerobics class - lay flat on your back with your legs straight up in the air, then flex your feet and then point your toes - do both feet at the same time then alternate feet, then hold them flexed, then hold them pointed. Do this for several 8 or so repetitions - works wonders!