The Achilles tendon is the thickest and strongest tendon in the human body. The Achilles tendon is about 15cm long and is formed by the fusion of the tendons of the triceps muscles of the calf (flounder, gastrocnemius internal and external head). In the process, the tendon fibers of the Achilles tendon have a 90° twist. The primary function of the Achilles tendon is to flex the calf and plantar-flex the ankle, and it is the most important anatomical structure for transmitting force from the calf muscles to the foot. People can stand upright, stand firm, run, jump, rely on it .