Your Achilles Tendon is the thick cord like structure you can feel at the back of your heel. It is part of your calf muscles (gastrocnemius and soleus muscles) and attaches these muscles to your heel bone (the calcaneus). When your calf muscles contract, your Achilles pulls on your heel bone to bend your foot and ankle towards the ground - a movement called plantarflexion.
Tendinitis is a condition that occurs when your tendon becomes inflammed or irritated. Achilles tendinitis, or inflammation in the Achilles tendon, is a relatively common condition. It can affect people at any age, however it tends to occur more frequently as you get older.
For most people, Achilles Tendinitis is short-lived and easily treated with rest and over-the-counter pain-relieving medications. Occasionally, the tendon becomes damaged by the inflammation, resulting in persistent pain or a tear (Achilles tendon rupture).