I finally had an MRI done on my ankle. I have a bone spur that may be causing an impingement at the front of my ankle (this was what was suspected based on my X-ray). However, it also shows osteoarthritis of the ankle (talonavicular joint) likely a result of a 1988 ankle break/dislocation, i.e., posttraumatic osteoarthritis.
If the pain I'm experiencing is due to the impingement, it may be possible to do surgery to remove the bone spur and clean that area out, thus improving range of motion and relieving my pain. If the pain is due to the OA, then there's not so much that can be done medically. I simply have to obey my pain when I run. Considering that I can run anywhere between 3 and 6 miles without significant pain, this is not terrible news. I can still run. Considering that I want to run longer (marathon or half marathon) distances, this is not great news. I cannot run very long.
I've got appointments with two surgeons to review the MRI results and discuss my options. I'm not sure how or if they can pinpoint the cause of the pain, but I'll see what they say and go from there.