Morphological study of the medial collateral ligament epiligament tissue in human

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The medial collateral ligament is one of the most commonly injured ligamentous structures of the knee joint, which predominantly occurs in young individuals, as a result of a valgus force on the knee during sports activities. The incidence of this injury has increased in recent years and presents a commonly encountered problem in modern sports medicine. Our recent reports in rat models demonstrate that fibroblasts in the epiligament, an enveloping tissue of the ligament, are not static cells and play an important role during the healing of the collateral ligaments of the knee. The aim of this study was to determine the normal morphology of the epiligament tissue of the medial collateral knee ligament in human.Several pieces of the mid-substance of the medial collateral ligament of the knee joint from 7 cadavers (3 females and 4 males) were taken.Our study demonstrated that the external surface of the epiligament was comprised of fbroblasts, fbrocytes, adipocytes, neuro-vascular bundles and numerous multidirectional collagen fibres. In the ligament, a classic morphological structure was found. It was poorly vascularized, composed of fascicles, which were formed by longitudinal groups of collagen fibres. Each fascicle appeared hypo-cellular in comparison to the epiligament and the cells were aligned in an interspersed pattern between bundles of collagen fibres.In conclusion, this study illustrates that the epiligament is a quite different structure from the ligament. It is composed of numerous fibroblasts, fibrocytes, adipocytes, and neuro-vascular bundles. The collagen fibres in the EL are multidirectional unlike those in the ligament substance. We also observed that the main part of the vessels of the epiligament-ligament structure was situated in the epiligament tissue.