In plantar fasciitis, the muscle band beneath the foot may perhaps build tiny tears and inflammation from recurrent strain, leading to pain and swelling inside the foot. It may affect a single foot or both equally ft. There is usually pain from the Achilles tendon insertion in to the calcaneus (heel bone) posteriorly (guiding). https://www.theorthopaedicandpainpractice.com/why-does-the-back-of-my-heel-hurt/