Study of the Nerve Endings and Mechanoreceptors of the Anterolateral Ligament of the Knee

Purpose: To describe the morphology and distribution of the anterolateral ligament of the knee (ALL) nerve endings, aiming to understand the interaction between the proprioceptive system and knee mechanics. Methods: Twenty ALLs were obtained from fresh frozen cadavers. The ligaments were measured, weighed, and cut. Sections (10 mu m) were prepared in hematoxylin and eosin-stained slides to analyze tissue integrity, and 50-mu m sections were subjected to immunofluorescence with the protein gene product 9.5 as primary antibody and Alexa Fluor 488 as secondary antibody, followed by microscopic analysis. Results: The ALL was identified in 100% of the dissections, exhibiting a mean (+/- standard deviation) length of 4.0 +/- 0.4 cm, a mean width of 5.5 +/- 0.8 mm, and a mean weight of 0.9 +/- 0.2 g. The histological sections in hematoxylin and eosin showed dense, well-organized collagen and the presence of vascular tissue. All the specimens analyzed contained type I (Ruffin-like) mechanoreceptors and free nerve endings (type IV), varying from parallel to intertwined fibers. Unclassified nerve endings with different irregular shapes were also found. The neural elements occupied 0.6% +/- 0.3% of the ligament area, and most were observed near the origin of ALL insertions. Conclusion: The ALL exhibits a peripheral nerve structure, primarily type I and IV mechanoreceptors. These findings suggest that the ALL is important for the proprioception and anterolateral stabilization of the knee.