The Achilles tendon is at the back of the heel. It connects to your calf muscle, which is why sprinting and jumping athletes are affected. The tendon can be ruptured by sudden force on the foot or ankle. If your Achilles tendon is ruptured you will be unable to stand on tiptoe and will have a flat-footed walk. It is important to diagnose and treat this injury as soon as possible, to help promote healing.