outer side of foot
I am a runner and began experiencing this problem several weeks ago. It occurs after I run. The further I run, the longer the pain lasts. Resting the foot for several days alleviates the pain, but it comes back when I try running again. On a treadmill, the problem seems less severe. But when running outside on uneven surfaces that cause the foot and ankle to turn as I step, the pain is worse, especially if the outer side of the foot is caused to angle upwards (ankle rotates towards the inside). In these instances it takes longer for the soreness to subside - noramlly 2 or 3 days. There is no swelling or discoloration - just the pain. Any idea what the problem could be?
Most likely an irritation of the peroneus longus tendon as it courses down the side of the foot and then takes a sharp turn under the foot. (I will assume the pain is where the side of the foot flares out a bit).
When you run on any kind of incline that supinates your foot such as a banked street it puts even more pressure on that side of the foot and will cause it to hurt more.
The more you pound it the more it hurts, commonsense! That is why it hurts less on the treadmill, your foot in not inclined.
If you are a runner, this could take forever to go away, but if you insist on running, I would stay on the treadmill for a while, obviously avoid the inclined and uneven surfaces outside, try a course of anti-inflammatory medication (if you can tolerate it) and perhaps a round of physical therapy, especially if you want this to resolve as quickly as possible.
Lastly, make sure your running shoes are wide enough at the flare of side of the foot; shoes can also be a major contributing factor.
Marc Mitnick DPM