Plantar fasciitis is seemingly caused by tissue fatigue in the arch of the foot due to excessive strain, plus probably some vulnerability due to a variety of biological or pathological factors that are usually unknown and probably often unknowable. Genetics are likely part of the mix. Not everyone who asks a lot of their feet gets plantar fasciitis; some lucky jerks can abuse their arches with impunity!
If the arch of your foot is like a bow, think of the plantar fascia as the bow’s string. The plantar fascia, along with several muscles both in the foot and in the leg, supports the arch and makes it springy.
Too springy, and the foot flattens out, overstretching the plantar fascia. Not springy enough, and the plantar fascia absorbs too much weight too suddenly.
Either way, it starts to burn with the strain.
Other than the fact that it’s on the bottom of your foot and you step on it a lot that’s the easy part of this equation to understand why is the plantar fascia vulnerable to strain? Why exactly? What happens?
Source: painscience.com