The Achilles tendon is a tough band of fibrous tissue that connects the calf muscles to the heel bone (calcaneus). The Achilles tendon is also called the calcaneal tendon.
The gastrocnemius and soleus muscles (calf muscles) unite into one band of tissue, which becomes the Achilles tendon at the low end of the calf. The Achilles tendon then inserts into the calcaneus. Small sacs of fluid called bursae cushion the Achilles tendon at the heel.
The Achilles tendon is the largest and strongest tendon in the body. When the calf muscles flex, the Achilles tendon pulls on the heel. This movement allows us to stand on our toes when walking, running, or jumping. Despite its strength, the Achilles tendon is also vulnerable to injury, due to its limited blood supply and the high tensions placed on it.