The Etiology And The Pathological Motion Of The Discoid Meniscus

Objective:The purpose of this study was to determine the etiology and the abnormal motion of the discoid lateral meniscus in the knee,and discussed the clinical meanings.Methods:(1)Our study was performed on 168 knees joints of 84 human foetus who were obtained from several local hospitals.After removal of the skin and muscles,the approach to the menisci was performed,opening anteriorly by a longitudinal incision on the joint capsule,cutting the patellar ligament and the cillateral ligaments transversely.In order to.expose the menisci clearly,the joint capsule and the intraarticular ligamnets were cut,and the femurs were separated.We measured the width of the midpoint of the anterior horns,bodies,posterior horns,and the lateral tibial plateaus.According to Chen Eryu's standards,the meniscal shape was classified as narrow shape,middle shape,wide shape,superwide shape and discoid shape. (2)12 discoid lateral menisci in 11 patients were examined,which were intact and can been observed snapping clearly.The knee was imaged in the sagittal plane while flexing from 0°to 45°and appearing snapping before and after.At the same time the discoid meniscal motional track and variation while appearing snapping were observed and measured.Result:(1)All the posterior horns of the lateral menisci are well attached to the posterior joint capsules.During the early stage of the human foetus,the discoid lateral menisci are mainly narrow shape and normal shape.With the increasing of months,the wide shape menisci have the tendence of enhancing.(2)we saw apparent difference between the abnormal motion of the discoid lateral meniscus and the motion of normal meniscus.During knee flexion the discoid lateral meniscus moved anteriorly.Furthermore,with the knee extension,at the time of occuring the snapping knee syndrome,the discoid lateral meniscus had a longger distance moving from posterior to anterior.(3)The arthroscopic meniscectomy can eliminate the abnormal motion of the discoid meniscus.Conclusion:(1)The discoid meniscus is congenital and formed in the period of embryononic life.(2)The development course of the discoid meniscus is from the infantile shape to the intermadiate shape,and the primitive shape is the last stage.(3)The discoid lateral meniscus with abnormal motion should undergo surgerical treatments at the early time.