The Achilles tendon of the lower extremity is subject to continued trauma with overuse due to excessive pronation -- inward rotation of the foot on the leg.

Achilles tendonitis has a characteristic cycle of great stiffness and pain the morning after walking or jogging.

Depending on the severity of injury, pain may be present at rest or after vigorous exercise.

There may also be localized swelling.

With Achilles tendonitis, there is usually an abnormal inward rolling of the foot. This inward rolling causes the muscles and tendons of the Achilles tendon to spasm as it tries to balance the foot.

This results in pain as the tendon becomes inflamed from the torque caused by the imbalance.

Some causes of Achilles tendonitis may include:

Running on flats instead of mixing the motion with some hills

Wearing shoes that cause the Achilles tendon to overstretch

Using a shoe with too much cushioning and not enough stability

Increasing your mileage log too quickly

Running on softer surfaces rather than hard surfaces

Worn shoes needing to be replaced

Lack of stretching tight muscles from running

The athlete should never attempt to "run through" the injured area.

Dr. Robert Weiss lives in Westport and has a podiatry practice in Darien. He is a veteran of 30 marathons and was a member of the Medical Advisory Committee of the 1984 and the 1988 U.S. Olympic Trials.