Histological and ultrastructural analysis of the knee anterolateral ligament

Abstract

The Anatomy of the lateral aspect of the knee has been increasingly debated in recent litera- ture, the morphology and function of anterolateral ligament (ALL) are not clearly understood even today (1, 2). The aim of present study was to provide for the first time a detailed ultras- tructural characterization of the ALL and its ultrastructure collagen arrangement using the light microscopy (LM), the transmission electron microscopy (TEM) and variable pressure scanning electron microscopy (VP-SEM). Eight paired samples from four fresh-frozen males cadavers were used for the study. Samples were harvested from the ALL, from the anterolateral capsule and from the medial collateral ligament (MCL). All samples were treated for microscopy tech- niques. Histological analysis showed similar morphology features between ALL and MCL sec- tioning, but clear differences are evident in comparison to the knee capsule. At TEM the colla- gen fibers of ALL and MCL showed similarity in the ultrastructural morphology, both collagen fibers have parallel alignment mainly orientated longitudinally. Significant structural difference of the tissue of the fibrous capsule compared to the ligaments may be observed. The VP-SEM highlighted that ALL and MCL morphology has shown aligned arrangements of fiber bun- dles densely packed, completely different assembling organization of the fibers were observed in fibrous capsule. Data from this study demonstrate that the ALL and MCL have compara- ble ultrastructural properties. It can further lead us to speculate that the ALL is a ligamentous structure distinct from the knee capsule.