As "overuse" disorders, Achilles tendonitis and tendonosis are usually caused by a sudden increase of a repetitive activity involving the Achilles tendon. Such activity puts too much stress on the tendon too quickly, leading to micro-injury of the tendon fibers. Due to this ongoing stress on the tendon, the body is unable to repair the injured tissue. The structure of the tendon is then altered, resulting in continued pain.
Athletes are at high risk for developing disorders of the Achilles tendon. Achilles tendonitis and tendonosis are also common in individuals whose work puts stress on their ankles and feet, such as laborers, as well as in “weekend warriors”—those who are less conditioned and participate in athletics only on weekends or infrequently. In addition, people with excessive pronation (flattening of the arch) have a tendency to develop Achilles tendonitis and tendonosis due to the greater demands placed on the tendon when walking. If these individuals wear shoes without adequate stability, their overpronation could further aggravate the Achilles tendon.
In diagnosing Achilles tendonitis or tendonosis, the surgeon will examine the patient’s foot and ankle and evaluate the range of motion and condition of the tendon. The extent of the condition can be further assessed with x-rays or other imaging modalities.
The symptoms associated with Achilles tendonitis and tendonosis include:
- Pain—aching, stiffness, soreness or tenderness—within the tendon. This may occur anywhere along the tendon’s path, beginning with the tendon’s attachment directly above the heel upward to the region just below the calf muscle. Pain often appears upon arising in the morning or after periods of rest, then improves somewhat with motion but later worsens with increased activity.
- Tenderness, or sometimes intense pain, when the sides of the tendon are squeezed. There is less tenderness, however, when pressing directly on the back of the tendon.
- When the disorder progresses to degeneration, the tendon may become enlarged and may develop nodules in the area where the tissue is damaged