Achilles tendonitis is a common condition in which inflammation of the Achilles tendon causes pain along the back of the ankle, near the heel, especially during walking and running. The Achilles tendon is a thick band of tissue that connects your calf muscles to your heel bone. It helps to balance forces in the leg and assists with movement of the leg and the ankle joint. Although the tendon can withstand great stress, it is also prone to tendonitis/tendinopathy, a condition associated with overuse and degeneration. This condition occurs when the demand placed on the Achilles tendon is greater than its ability to function. It can also result from, calf weakness or tightness, wearing improper footwear, abnormal foot mechanics, a change in an exercise routine or sports activity. Common symptoms include swelling, tenderness and tightness along back of heel or ankle, and severe pain after exercising.