Achilles tendon

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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 .

Gross anatomy

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 ).

Function

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 .

Related pathology

  • calcaneal tendon tear: may be microtears or large, either complete or incomplete; it may occur suddenly during sports or gradually
  • calcaneal tendon rupture: occurs 2-6 cm proximal to the calcaneus; it occurs within the hypovascular watershed zone
  • calcaneal tendinitis: is inflammation within the tendon itself, which may swollen with abnormal internal signal (MRI)
  • calcaneal tendon ossification
  • calcaneal peritendinitis: inflammation in the structures surrounding the tendon, usually ≥5 cm above the heel
  • calcaneal tendinosis: gradual thickening of the tendon without visible inflammatory process; even though the tendon is thick, it is weak and more vulnerable to tear
  • calcaneal tendinopathy: is broad terminology that encompasses tendinitis and tendinosis
  • calcaneal enthesopathy

History and etymology 

The oldest written record for the term Achilles being used to describe the calcaneal tendon was in 1693 by Flemish/Dutch anatomist Philip Verheyen in his text Corporis Humani Anatomia. The use of the term itself is based on the Greek myth of the warrior Achilles .