The Achilles tendon is a strong band of tissue that joins the calf muscles to the calcanues, or heel bone. This tendon shortens whenever the toes are pointed, and stretches when the toes are flexed. Activities that involve repetitive pounding and stress on the feet, such as running and jumping, can lead to injuries of the Achilles tendon. According to the American College of Foot and Ankle Surgeons, Achilles tendinitis refers to inflammation of the tendon, which, if left untreated, can lead to Achilles tendinosis, or degeneration of the tendon. Achilles tendinosis may present with the pain and stiffness of tendinitis, or it may be relatively asymptomatic, with the only indicators of dysfunction being painless changes to the tendon fibers.
Pain
Sometimes, Achilles tendinosis may present with pain. Because of the micro-tearing that occurs within the tendon fibers, the Achilles can hurt anywhere from its origin about two-thirds of the way down the back of the lower leg to its insertion into the heel bone. The American College of Ankle and Foot Surgeons explains that pain is often worse when getting out of bed first thing in the morning, or after long periods of sitting or resting, and also after periods of overuse. The pain might be described as soreness, tenderness, or twinging, and is often exacerbated when the sides of the affected Achilles tendon are squeezed.
Stiffness
Chronic stiffness in the Achilles region can also suggest Achilles tendinosis. Stiffness is typically worse after periods of inactivity, and the affected side may feel like there's a constant stretch or tautness just above the heel.
Tendon Changes
During Achilles tendinosis, collagen degeneration occurs, causing changes in the appearance and feel of the tendon itself. As the American Academy of Family Physicians explains, the tendon will enlarge in a diffuse manner. If calcification of the tendon also occurs, the tendon will have palpable nodules along its length. According to assistant professor Laura M. Gottschlich at the Medical College of Wisconsin, sometimes a sensation of fullness and the palpation of a thickened, nodular tendon may be the only symptoms of Achilles tendinosis.
