Achilles tendon

US /əˌkɪl.iːz ˈten.dən/
UK /əˌkɪl.iːz ˈten.dən/
"Achilles tendon" picture
1.

a large tendon that runs from the calf muscle to the heel bone

:
He ruptured his Achilles tendon playing basketball.
Pain in the Achilles tendon can be a sign of overuse.