Achilles Tendon

Achilles insertional tendinopathy (AIT) is a tendon problem commonly found in both elite and recreational athletes. Unlike Achilles peritendinitis and mid-substance tendi-nosis where the changes are generally found 2 to 6 cm proximal to the calcaneal insertion, AIT is by definition seen directly adjacent to the calcaneus.5,7 Patients are symptomatic with posterior heel pain limiting jumping and running abilities. The condition is disabling and chronic for the involved athlete, often requiring months of limited activities and recovery time. Although AIT is well recognized as a distinct disorder, surprisingly little is known about its cause. It is generally considered an overuse injury, and certain factors are often mentioned as predisposing factors.4 Overuse due to rapid changes in duration and/or intensity of exercise is thought to place repetitive tensile loads on the tendon that lead to an accumulation of micro injuries. Predisposing factors that are mentioned include poor shoe design, foot and ankle malalignment, inflexibility, muscle weakness, age, and poor vascular supply. However, there are no controlled studies available that study the theory of repetitive tensile loads as the biomechanical cause.2 The goal of this biomechanical study was to investigate strains in the distal Achilles tendon under simulated mus-cular loading conditions through a functional range of ankle motion. It was hypothesized that the anterior portion of the tendon is loaded preferentially as would be evi-denced by higher strains compared to the posterior aspect. This would explain the clinical finding of abnormalities to the anterior part of the tendon in most patients with AIT (see Fig. 1). A secondary goal was to establish normativ