Collagen-elastin microstructural network and its mechanical implications in the anterior cruciate ligament

Background Understanding the microstructural basis of anterior cruciate ligament (ACL) mechanics is important for advancing reconstruction strategies and rehabilitation. Histological studies indicate that collagen and elastin are distributed in a region-specific manner within the ligament, but such heterogeneity has rarely been incorporated into computational models. Finite element (FE) simulations are widely applied in ligament biomechanics, yet their validation against clinically used tools such as the Lachman test with KT2000 arthrometry remains limited. This study aimed to investigate how regional collagen–elastin variations affect ligament mechanics, whether histology-informed models provide improved agreement with experimental data, and how closely such models align with clinical assessment. Methods Porcine ACLs were selected as surrogates for the human ligament due to their structural similarity. Regional collagen and elastin distributions were quantified using histological imaging and integrated into a crosslinked collagen–elastin fiber network model. Finite element analyses were performed under tensile, shear, and torsional loading. Model predictions were compared with uniaxial tensile testing of ACL specimens and with force–displacement curves obtained from KT2000 arthrometry during Lachman testing. Simulations were conducted at both millimeter and micrometer scales to assess multi-scale applicability. Results The histology-informed fiber model reproduced ligament stiffness more consistently than a uniform sheet representation, particularly under tensile loading. Its stiffness characteristics showed partial agreement with experimental uniaxial data and with KT2000 arthrometer measurements in normal and injured knees. Comparable outcomes across different model scales suggested that the framework is adaptable to multi-scale analyses. Conclusion This study highlights the contribution of region-specific elastin distribution to ACL mechanical behavior and demonstrates that histology-informed FE models may improve biological relevance compared with uniform representations. While still preliminary, the partial alignment with both experimental and clinical measurements suggests that such models may provide a useful foundation for bridging microstructural mechanics and joint-level function. With further refinement, this approach could support individualized planning, rehabilitation monitoring, and the design of biomimetic grafts.