Unveiling the sensory architecture of the medial collateral ligament epiligament: A morphological study with clinical relevance.

Abstract

This cadaveric descriptive study was aimed at evaluation of the nerve fibers and mechanoreceptors of the epiligament of the medial collateral ligament (MCL) of the human knee - their distribution, density and potential clinical implications. Tissue samples were obtained from 12 fresh cadavers, and 5-μm sections corresponding to the proximal, mid, and distal portions of the epiligament were stained with hematoxylin and eosin, Luxol fast blue/Cresyl violet, and antibodies against S100B and myelin basic protein. ANOVA and post hoc Tukey tests were used to assess the differences in density distributions of the neural elements in the different portions of the epiligament. The proximal region of the epiligament exhibited the highest density of both myelinated and unmyelinated nerve fibers and Meissner's corpuscles, followed by the distal region, while the mid-portion, despite a lower density, contained larger-caliber nerve fibers -suggesting that primary nerve branches enter through the mid-region and subsequently branch into smaller fibers towards the proximal and distal areas. This investigation is the first to document the presence of Meissner's corpuscles within the epiligament of the MCL, thereby expanding our understanding of ligament mechanoreception. These findings underscore the pivotal role of the epiligament in mediating mechanoreception, nociception, proprioception, and blood flow regulation, and highlight its potential impact on ligament regeneration and post-surgical outcomes. Overall, our study advances the current knowledge of MCL innervation and lays the groundwork for future research into its therapeutic implications in knee joint biomechanics and ligament healing.