The Achilles tendon is at the back of the heel. It 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. Treatment involves wearing a plaster cast or brace (orthosis) for several weeks, and possibly having an operation.