Dr. Burton S. Schuler, explains Tendinitis

Tendinitis is a stressing or straining of a muscle or group of muscles which results in severe pain and or swelling. The most common tendinitis in the foot is found in the Achilles tendon. The Achilles tendon starts at the calf muscle then runs down the back of the leg into the heel bone. The major reason a tendon in the foot will become inflamed is due to overuse via Abnormal Pronation; that ia caused by a Morton’s Toe. Tendinitis can also be a side effects of Arthritis or Diabetes.
Many people have short Achilles tendons due to wearing high heel shoes. Over a period of time the tendon becomes shorter because it is not being stretched. But this can be reversed with stretching exercises of the Achilles. The best way to treat this problem if the cause is due to Abnormal Pronation is to control it by making an Orthotic.
Other treatments for tendinitis include Physical Therapy, padding and strapping of the feet/heel, and anti-inflammatory medications. The good news is surgery is rarely needed for Achilles tendinitis.