Achilles tendon 
noun
The tendon connecting calf muscles to the heel.A common sprain injury is a torn Achilles tendon, which connects the calf muscles to the heel....
- This is especially true if the rupture is in the Achilles tendon, the tendon just above the heel.
- Ankle and ligament damage is also common, as well as Achilles tendon rupture and calf tendon tears.