The tendo Achillis as it relates to rearfoot position. A new classification for evaluation of calcaneal stance position.

In summary, it has been demonstrated by the statistical analysis of 48 subjects (96 feet) that as the foot moves from the neutral to the resting calcaneal stance position, the tendo Achillis alignment is displaced lateral to the center of gravity. Class I heels demonstrated a direct correlation with tendo Achillis deviation suggesting that their subtalar joint motion is in the transverse plane. Class II and III heels did not directly correlate with Achilles deviation, suggesting probable frontal plane variability. Class IV heels showed no correlation with rearfoot pathology and are considered to be a consequence of distal or proximal pronatory forces. We advocate the recognition of the Achilles tendon as it interacts with transverse and frontal plane subtalar joint motion and believe that it deserves ample attention when evaluating the patient biomechanically as well as surgically.