Meniscal anatomy

Abstract

The menisci are fibrocartilaginous structures within the knee joint that play important roles in the normal function of the knee. The menisci arise from mesenchymal progenitor cells in the limb bud and become distinct structures by the 8th week of gestation. The fibrochondrocyte is the primary cell type of the meniscus, and these cells are arranged in a complex manner which, along with the extracellular matrix, forms the basis of the mechanical properties of the meniscus. The extracellular matrix is composed of ~ 70 % water and ~30 % collagen and proteoglycans. The medial and lateral menisci differ in size and shape, and their dimension is correlated to gender, height, and weight. The menisci are attached within the joint primarily by bony attachments of the anterior and posterior horns with accessory structures providing some stability. The medial meniscus has more soft tissue and bony connections than does the lateral meniscus and, therefore, plays a more important role in joint stability. While the entire meniscus is vascular early in development, the vascular supply in the adult meniscus occurs only in the periphery which has important implications in the treatment of meniscal tears. The majority of the meniscus is void of any neural elements; however, mechanoreceptors and sensory fibers can be found in the periphery and contribute to proprioception of the knee and along with capsular irritation, the cause of pain in meniscal tears.