Displacement profiles across morphological variations of the Achilles tendon. A:The reference Achilles model includes twisted subtendons, inter-subtendon sliding, and a retrocalcaneal insertion. B: Without this insertion, the model displays nonuniform displacements. C: Without twisted subtendons, the differential displacements in the free tendon are slightly reduced. D: In the absence of sliding, differential displacements between subtendons are negligible.