Overview of Achilles Tendonitis

Achilles tendonitis, also sometimes called Achilles tendinitis, is a painful and often debilitating inflammation of the Achilles tendon (heel cord). The Achilles tendon is the largest and strongest tendon in the body. It is located in the back of the lower leg, attaches to the heel bone (calcaneus), and connects the leg muscles to the foot.

The Achilles tendon gives us the ability to rise up on our toes, facilitating the act of walking, and Achilles tendonitis can make walking almost impossible.


Side View of Foot
Back View of Foot
& Calf Muscles
Side View of Foot
Back View of Foot
Click on the images to view a larger version.

There are three stages of tendon inflammation:

  1. Peritenonitis
  2. Tendinosis
  3. Peritenonitis with tendinosis

Peritenonitis is characterized by localized pain during or following activity. As this condition progresses, pain often develops earlier on during activity, with decreased activity, or while at rest.

Tendinosis is a degenerative condition that usually does not produce symptoms (i.e., is asymptomatic). It may cause swelling or a hard knot of tissue (nodule) on the back of the leg.

Peritenonitis with tendinosis results in pain and swelling with activity. As this condition progresses, partial or complete tendon rupture may occur.

Incidence and Prevalence of Achilles Tendonitis

The overall incidence of Achilles tendonitis is unknown. The condition occurs in approximately 6–18 percent of runners, and also is more common in athletes, especially in sports that involve jumping (e.g., basketball), and in people who do a lot of walking.

Achilles tendonitis that occurs as a result of arthritis in the heel is more common in people who are middle aged and older.

Publication Review By: Hai-En Peng, D.P.M.

Published: 31 Dec 1999

Last Modified: 23 Sep 2014