Discoid lateral meniscus in children and adolescents: a histological study

BACKGROUND: Discoid lateral meniscus is the most frequent variant of the meniscus. Although the histology of normal menisci in children and in adults has been well described, few studies have focused on the histology of discoid menisci. Furthermore, most of the patients in those studies were adults. The aim of the present study was to report the histological findings of discoid lateral meniscus in a group of children and adolescents, aged between 9 and 18, after arthroscopic partial resection, focusing on cellularity, arrangement of collagen fibers, and vascularity of the excised fragments. Furthermore, to report on MRI findings compared to the histological findings in the same region. METHODS: Six patients (one female and five males) aged 9, 10, 13, 15, 17, and 18, were arthroscopically operated on partial meniscectomy (saucerization) of a discoid lateral meniscus, and the specimens were histologically examined. RESULTS: The extracellular matrix showed a different distribution and characteristics depending on the different side of the meniscus. Irregularly oriented collagen fibers in discoid lateral meniscus were found. There were no blood vessels in the inner part of discoid lateral meniscus in all patients but the 18-year old (in which we observed also endothelials cells, edematous tissue and leaking of erythrocytes in the extracellular matrix). In the discoid lateral menisci analyzed, irregularly oriented collagen fibers with blood vessels were found only in the presence of degenerating tissue. CONCLUSIONS: Discoid lateral meniscus is different from a normal meniscus in terms of vascularity and disorganization of collagen fibers.