Discoid mensicus is a dysplastic meniscus that has lost its normal semilunar shape. It is more common in lateral meniscus than medial one. It presents clinically as asymptomatic snapping of the knee in the last few degrees of extension. It is usually discovered accidentaly on doing arthroscopy for other reason. It may be complete, incomplete or wrisberg ligament type in which there is absence of the posterior meniscotibial attachment results in abnormal hypermobility of the central portion of the meniscus towards the intercondylar area of the proximal tibia. This results in by pertrophy of the meniscus the discoid meniscus being larger and thicker than normal is susceptible to tears and degenerative changes than normal meniscus.
The most conclusive method of diagnosis is MRI examination of the knee. Showing in sagittal images loss of the normal bow-tie appearance of meniscus. In coronal images the discoid meniscus is seen abnormal encroaching towards the intercondylar notch of the tibia.
Asymptomatic cases needs no treatment. Symptomatic cases with picture of tear, degeneration or chronic pain need surgical intervention. Complete and incomplete types need partial meniscectomy in which the central part of the meniscus only is removed leaving a stable peripheral rim. This part is removed in piece-meal fashion, in one piece or in two pieces. The wrisberg ligament type needs total meniscectomy.
Conclusion :
The discoid meniscus is more common than clinical statistics indicate. It is diagnosed accurately and easily with MR imaging of the knee. Treatment modalities are various. The arthroscopic treatment of the torn discoid meniscus is more difficult than that of the normally formed meniscus.
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