Nanoscale characterization of collagen structural responses to in situ loading in rat Achilles tendons
Journal article, 2023

The specific viscoelastic mechanical properties of Achilles tendons are highly dependent on the structural characteristics of collagen at and between all hierarchical levels. Research has been conducted on the deformation mechanisms of positional tendons and single fibrils, but knowledge about the coupling between the whole tendon and nanoscale deformation mechanisms of more commonly injured energy-storing tendons, such as Achilles tendons, remains sparse. By exploiting the highly periodic arrangement of tendons at the nanoscale, in situ loading of rat Achilles tendons during small-angle X-ray scattering acquisition was used to investigate the collagen structural response during load to rupture, cyclic loading and stress relaxation. The fibril strain was substantially lower than the applied tissue strain. The fibrils strained linearly in the elastic region of the tissue, but also exhibited viscoelastic properties, such as an increased stretchability and recovery during cyclic loading and fibril strain relaxation during tissue stress relaxation. We demonstrate that the changes in the width of the collagen reflections could be attributed to strain heterogeneity and not changes in size of the coherently diffracting domains. Fibril strain heterogeneity increased with applied loads and after the toe region, fibrils also became increasingly disordered. Additionally, a thorough evaluation of radiation damage was performed. In conclusion, this study clearly displays the simultaneous structural response and adaption of the collagen fibrils to the applied tissue loads and provide novel information about the transition of loads between length scales in the Achilles tendon.

Achilles tendon

Collagen structure


Small-angle X-ray scattering

In situ loading


Isabella Silva Barreto

Institutionen för Biomedicinsk Teknik

Maria Pierantoni

Institutionen för Biomedicinsk Teknik

Malin Hammerman

Institutionen för Biomedicinsk Teknik

Linköping University

Elin Törnquist

Institutionen för Biomedicinsk Teknik

Sophie Le Cann

Laboratoire Modélisation et Simulation Multi Echelle (MSME)

Ana Diaz

Paul Scherrer Institut

Jonas Engqvist

Lund University

Marianne Liebi

Paul Scherrer Institut

Swiss Federal Laboratories for Materials Science and Technology (Empa)

Chalmers, Physics, Materials Physics

Pernilla Eliasson

Linköping University

Sahlgrenska University Hospital

Hanna Isaksson

Institutionen för Biomedicinsk Teknik

Matrix Biology

0945-053X (ISSN) 15691802 (eISSN)

Vol. 115 32-47

Subject Categories

Applied Mechanics

Bio Materials

Other Materials Engineering





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