Should I repeat it? This injury is one of the most uncomplicated injuries to fix, yet so many people suffer from no clear direction or clue how to cure it. Look no further, boys & girls. Those days are long gone. 

First, we need to understand what is going on mechanically & how it is essentially a "Tug of War" from hell, causing your foot & ankle pain.

The achilles tendon attaches to your heel bone, and the plantar fascia does the same (this is a simplified version of the story, so physio's don't go crazy.) When the achilles gets tight, it pulls on the heel bone. Since all shoes have a heel drop and place the heel higher than the front of the foot - losing ROM here is typical. The plantar fascia (arch of your foot on the bottom side) also gets tight and starts to pull on the same bone. This is where the "Tug of War" begins. Who do you think will win? The strong achilles that attaches into the Soleus and Calf muscle, or the minor plantar fascia? 

The plantar fascia has no chance, and the heel bone begins to rotate back due to the tension of the achilles. Since bone is the most sensitive tissue in the body and now your plantar fascia is losing the fight, it makes complete sense why that one spot on the bottom side of your foot begins to catch fire. It is the same spot that feels like it's stuck with a knife when you get out of bed. If this is allowed for too long, it is not uncommon for a bone spur to begin taking place. This is your heel bone's last-ditch effort to relieve the pressure/shortness of the plantar fascia. It is creating a ladder or bridge to keep it attached. That is why it looks like a bony growth on an X-ray - because it is.