Achilles tendonitis 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. The condition occurs in approximately 6–18% 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.
Poorly conditioned athletes are at the highest risk of developing Achilles tendonitis. Participating in activities that involve sudden stops and starts and repetitive jumping (e.g., basketball, tennis, dancing) increases the risk for the condition. It often develops following sudden changes in activity level, training on poor surfaces, or wearing inappropriate footwear.
Stages of Achilles Tendonitis
There are three stages of tendon inflammation:
- 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.
Achilles tendonitis may be caused by a single incident of overstressing the tendon, or it may result from a series of stresses that produce small tears over time (overuse).
The condition also may develop in people who exercise infrequently and in those who are just beginning an exercise program, because inactive muscles and tendons have little flexibility because of inactivity. It is important for people who are just starting to exercise to stretch properly, start slowly, and increase gradually.
Patients who develop arthritis in the heel have an increased risk of developing Achilles tendonitis. This occurs more often in people who middle aged and older.
In some cases, a congenital (present at birth) condition causes Achilles tendonitis. Typically, this is due to an abnormal rotation of the foot and leg (pronation), which causes the arch of the foot to flatten and the leg to twist more than normal.
Women who wear high-heeled shoes often and switch to sneakers for exercise also can develop Achilles tendonitis. The Achilles tendon and lower leg muscles gradually adapt to a shortened position because the shoes prevent the heel from stretching all the way to the ground. If high heels are worn every day, stretching should be done every morning and night to keep the Achilles tendon lengthened.