I didn't know what this was until a couple of days ago. Now I do because I damaged the left one walking in the Luss Hills. It's the tendon that runs down the front of the shin to the ankle and is involved in lifting up the foot, so pretty important for walking.
At the moment, walking becomes difficult and painful after a couple of minutes. The doctor reckons it should clear up in a couple of weeks and has prescribed strong anti-inflammatory painkillers, ice packs and rest. However it could take much longer, especially if it's been caused by a longer-term muscle imbalance or foot problem. Only time will tell.
This is the last thing I needed, five weeks before I'm due to set off.