Morphology of the medial meniscus of the knee in human fetuses.

OBJECTIVES The objectives were to study the morphology of the medial menisci in human fetal knee joints and to verify the developmental etiology of the discoid meniscus. MATERIAL AND METHODS The study was carried out on 106 fetal knee joints and the morphological variants of the shapes of the medial menisci were macroscopically noted and classified. RESULTS From our observations, 46.2% of the medial menisci were crescentic shaped, 23.6% were sided V-shaped, 13.2% had sided U-shape, 9.4% of them were sickle shaped, and 7.5% were C-shaped. In 54.71% of the cases, the medial meniscus shape was different on either side knees of the fetuses. No discoid medial menisci were seen. CONCLUSIONS The majority of the knees were having crescentic or semi lunar shaped medial menisci and the shape of the medial meniscus was different on right and left side knee joint of the fetuses in more than fifty percent of the cases. The observations favor Kaplan's theory, as there were no discoid medial menisci observed from the fetuses of various gestational ages. Even the youngest fetus (CRL 88 mm, 14 weeks of gestation) exhibited the medial tibial plateau incompletely covered by the menisci, which did not exhibit the discoid shape. The discoid meniscus must be an abnormal finding and is due to abnormal morphogenesis.