Achilles Tendonitis: Inflammation of your Achilles tendon, connecting the calf muscle into the heel bone, typically caused by overuse. This leads to pain and stiffness in the back with the heel, Specially throughout action. Working out what causes sciatica is the initial step in understanding and dealing with this situation. https://www.theorthopaedicandpainpractice.com/why-does-the-back-of-my-heel-hurt/