The outer rim is wider and better supplied with fibres and blood vessels.
The lateral (outer) meniscus is more 'O-shaped' than the medial meniscus, which is more 'C-shaped'. At the far ends are the two 'horns'.
Areas of the outer rim, especially on the medial meniscus, are intimately related to the capsule.
What does the knee meniscus do?
The menisci are the shock absorbers of the knee. Their crescentic shape, with a wider outer rim and a flattened inner rim, allow them to absorb the vertical forces going through the joint channelling the forces towards the outer edge where the fibre bundles are more tightly packed and which thus takes most of the stress.
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A Current Review of the Meniscus Imaging: Proposition of a Useful Tool for Its Radiologic Analysis. Lefevre N, Naouri JF, Herman S, Gerometta A, Klouche S and Bohu. Radiol Res Pract. 2016; 2016: 8329296..