Tibialis posterior tendon
The bright side is that this problem has been picked up and you are on the treatment path. Tib post tendon dysfunction is the most common cause of adults who acquire a flat foot. This occurs if the early rupture is not diagnosed which would end up ruining your running permanantly. Hopefully this is only a partial rupture. The rehab is long and involved but you just have to work through this and come back stronger down the line
Hang in there, Traveler. I didn't tear mine but spent about 4mos this year treating posterior tib and achilles tendonitis in both legs. I know it's painful - physically and emotionally. All I can say is do whatever your doc and physio say and you'll be back on the trails next year.
Good luck!
"It's very hard in the beginning to understand that the whole idea is not to beat the other runners. Eventually you learn that the competition is against the little voice inside you that wants you to quit." ~George Sheehan



Just got diagnosed w/ a tear....MRI to confirm if partial or total tear next week. Anyone else ever gone through this before??? Im in a cast and the marathon i was training for is out the window now :(