Connective tissue attaches to bone across an insertion with spatial gradients in components, microstructure, and biomechanics. Due to regional stress concentrations between two mechanically dissimilar materials, the insertion is vulnerable to mechanical damage during joint movements and difficult to repair completely, which remains a significant clinical challenge. Despite interface stress concentrations, the native insertion physiologically functions as the effective load-transfer device between soft tissue and bone. This review summarizes tendon, ligament, and meniscus insertions cross-sectionally, which is novel in this field. Herein, the similarities and differences between the three kinds of insertions in terms of components, microstructure, and biomechanics are compared in great detail. This review begins with describing the basic components existing in the four zones (original soft tissue, uncalcified fibrocartilage, calcified fibrocartilage, and bone) of each kind of insertion, respectively. It then discusses the microstructure constructed from collagen, glycosaminoglycans (GAGs), minerals and others, which provides key support for the biomechanical properties and affects its physiological functions. Finally, the review continues by describing variations in mechanical properties at the millimeter, micrometer, and nanometer scale, which minimize stress concentrations and control stretch at the insertion. In summary, investigating the contrasts between the three has enlightening significance for future directions of repair strategies of insertion diseases and for bioinspired approaches to effective soft–hard interfaces and other tough and robust materials in medicine and engineering.

中文翻译：

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三种不同软组织-硬组织插入物的成分、结构和生物力学特性：比较综述

结缔组织通过插入物附着在骨骼上，并在成分、微观结构和生物力学方面具有空间梯度。由于两种机械上不同的材料之间存在区域应力集中，插入在关节运动过程中很容易受到机械损伤，并且难以完全修复，这仍然是一个重大的临床挑战。尽管界面应力集中，但天然插入在生理学上充当软组织和骨骼之间的有效负载转移装置。这篇综述对肌腱、韧带和半月板插入进行了横断面总结，这在该领域是新颖的。本文详细比较了三种插入物在成分、微观结构和生物力学方面的异同。本综述首先分别描述每种插入物的四个区域（原始软组织、未钙化纤维软骨、钙化纤维软骨和骨骼）中存在的基本成分。然后讨论了由胶原蛋白、糖胺聚糖（GAG）、矿物质等构建的微观结构，它为生物力学特性提供了关键支持并影响其生理功能。最后，该评论继续描述毫米、微米和纳米尺度的机械性能变化，这些变化最大限度地减少了应力集中并控制了插入处的拉伸。总之，研究三者之间的对比对于插入疾病修复策略的未来方向以及医学和工程中有效软硬界面和其他坚韧材料的生物启发方法具有启发意义。