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Illustration of Achilles Tendon

Picture of the Achilles Tendon

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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.

Achilles Tendon Conditions

  • Achilles tendon tear: Tears of the Achilles tendon can be tiny (microtears), or large, causing pain, swelling, and impaired movement. They may occur suddenly during activity, or gradually over time.
  • Achilles tendon rupture: A complete rupture of the Achilles tendon may make a "pop" sound, followed by pain and swelling of the lower leg. Treating an Achilles tendon rupture requires surgery or long-term immobilization of the ankle.
  • Achilles tendinitis (tendonitis): Frequent activity (running or walking) can gradually inflame the end of the Achilles tendon, causing pain and stiffness at the back of the heel. Rest, ice, and stretching may speed healing, which can take weeks.
  • Achilles peritendonitis: Similar to Achilles tendonitis, but inflammation and pain occur in the tissue surrounding the tendon, often two or more inches above the heel. 
  • Achilles tendinosis: Gradual thickening of the Achilles tendon without apparent inflammation, due to aging or overuse. Despite the thickening, the tendon is weakened and prone to further injury or rupture.
  • Achilles tendinopathy: A general term for tendinitis or tendinosis affecting the Achilles tendon.
  • Achilles or heel (calcaneal) bursitis: Low-riding shoes can irritate the bursa, a sac of fluid cushioning the Achilles tendon at the heel. Pain in the back of the heel, worse with shoes on, is the common symptom.

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