Grade: 3
This was the reason I didn't finish the 2008 double chubb 50k. Took about a month or two off, but it still comes back if I'm training pretty hard.
Now I think there's something wrong with the right ankle and it causing stuff to go wrong in the right leg. It seems to help if I have good arch support in my shoes or if I tape the arch of my right foot
See Posterior tibalis tendonitis