Pain in the tendon of the left heel may be caused by two conditions: 1. It may be Achilles tendonitis. This condition is usually more common in people who often run, or bounce and other sports. Because when doing these sports, due to the Achilles tendon with the heel node joint place is often strained, resulting in some small lacerations, over time to form a chronic sterile inflammation. If this inflammation is serious, there will also be local symptoms of redness, swelling, heat and pain. 2, there may be a strain of the Achilles tendon, this situation is to do strenuous exercise before the warm-up is not ready, or the explosive force at the time, resulting in a strain of the Achilles tendon. This condition will appear immediately during exercise, and there will be immediate local swelling, pain, and limited function of the activity.