Meniscus

If you have some water in a test tube or narrow pipette, you can see that the water appears to be sticking to the sides of the tube, forming a bowl-shaped curve called the meniscus. The meniscus is formed because the adhesion of the water molecules to the glass is greater than the cohesion of the water molecules to each other.

To measure the water in the tube, you measure up until the bottom of the meniscus.

If you have mercury in a tube, like in a thermometer, the mercury forms a meniscus that bulges in the opposite direction. The mercury has greater cohesion between its own molecules than it has adhesion to the glass. Measure from the bottom of the thermometer to the top of the mercury's meniscus.

It is possible to have a knee injury in which one or the other (or both, I guess) menisci are torn and possibly displaced. This is very painful, I kid you not. If part of the cartilage ends up in the wrong place inside the knee joint as a result of this tear, the leg may not straighten completely, and can get locked in a particular position. Did I mention the pain?

Treatment for a torn meniscus sometimes involves simply removing the torn bit (a meniscectomy) but can also involve surgical repair, in which the torn parts are stitched down in place with sutures or with some cute little bioabsorbable arrows that are shot out of a dispenser. The larger the torn fragment, the more likely a surgeon will attempt a repair. Knee joints with cartilage removed don't work very well or last very long.

YMMV, as IANAD.

Me*nis"cus (?), n.; pl. L. Menisci (-si), E. Meniscuses (#). [NL., from Gr. , dim. of mh`nh the moon.]

1.

A crescent.

2. Opt.

A lens convex on one side and concave on the other.

3. Anat.

An interarticular synovial cartilage or membrane; esp., one of the intervertebral synovial disks in some parts of the vertebral column of birds.

Converging meniscus, Diverging meniscus. See Lens.

© Webster 1913.