Achilles Tendon Rupture (Tear) The Achilles tendon is the largest tendon in the body. It connects your calf muscles to your heel bone and is used when you walk, run, and jump. Although the Achilles tendon can withstand great stresses from running and jumping, it is vulnerable to injury. A rupture of the tendon is a tearing and separation of the tendon fibers so that the tendon can no longer perform its normal function.