Calcaneal tendon

Last revised by Mostafa Elfeky on 13 Jul 2023

The calcaneal tendon, commonly known as the Achilles tendon, is the strongest and largest tendon of the human body. It is also one of the commonest tendons to become injured due to its high biomechanical load but poor vascularity 2.

The calcaneal tendon forms by the merging of fibers of the gastrocnemius and the soleus muscles, forming the tendon that inserts into the posterosuperior aspect of the calcaneus.

The proximal fibers of the calcaneal tendon have a rounded appearance that becomes relatively flat about four centimeters proximal to the insertion site. This alignment gives the tendon its spiral pattern that helps locomotion.

All the tendons that cross the ankle are enclosed within their own synovial sheath except for the calcaneal tendon, which has no covering surrounding synovial sheath but a posterior paratenon (so there is no calcaneal synovitis, but rather tendinitis or peritendinitis instead 1).

The calcaneal tendon enables the person to rise up on their toes and push forward during walking or running, to jump and land, as well as to climb and descend stairs 2.

The oldest written record for the term Achilles being used to describe the calcaneal tendon was in 1693 by Flemish/Dutch anatomist Philip Verheyen (1648-1710) in his text Corporis Humani Anatomia 4The use of the term itself is based on the Greek myth of the warrior Achilles, the hero of the Trojan War, whose whole body was invulnerable to all injuries, except for his heel. 

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Cases and figures

  • Normal Achilles tendon (US)
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  • Normal Achilles tendon (AP)
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  • Normal Achilles tendon (lateral)
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