Definition of Achilles Tendon

A thick, strong band of connective tissue at the back of the heel that joins the gastrocnemius and soleus muscles of the calf (back of the lower leg) to the calcaneus (heel bone). The Achilles tendon makes possible extension of the foot, a necessary element of walking, running, and jumping.

A sharp tap to the Achilles tendon with a reflex mallet causes the foot to jerk downward; this is the Achilles tendon reflex. Motor neuron diseases such as amyotrophic lateral sclerosis (ALS) and post-polio syndrome produce abnormal reflex responses.

Injury affects the ability to move the foot down. The tendon is vulnerable to damage during running and jumping, and especially “plant and twist” kinds of movements, common in numerous sports such as baseball, basketball, tennis, soccer, football, and running. The tendon may become inflamed (tendonitis) or tear (rupture).

For further discussion of musculoskeletal structure and function, please see the overview section “The Musculoskeletal System.”

See also ACHILLES TENDON INJURYLIGAMENT; POLIOMYELITIS.

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