I was diagnosed with this today. I had originally thought that I had torn/strained my Achilles and calf muscle. This diagnosis was, in fact, supported by my family doctor. However, after seeing a specialist today, I was diagnosed with a complete rupture of the plantaris tendon.
I did this 3 weeks ago while on a ROAD ride. I was pushing it pretty hard for a period of about 3 1/2 hours, and @ one point I felt a twinge/pop in my ankle. I didn't think much about it @ the time because there was no real pain. However, the next day the pain came in a big way. The pain started @ my heal, and ran through my calf. I've been treating it with R.I.C.E. ever since. I did try and ride on it a few times, but the pain came back after each ride.
Anywho, this is what I learned today:
The plantaris tendon runs on the inside of the Achilles tendon, and attaches to the medial side of the heal/Achilles tendon and the calf muscle. The bottom line is that this is not generally repairable. However, the good news is that one can get by without this tendon. There is a 6 week recovery period.
So ... has anyone else had this injury? If so, would you please comment?