What Is Torn Knee Cartilage (Meniscus Tears)?
There are two different mechanisms that result in a tear to a meniscus.
Traumatic tears result from a sudden load being applied to the meniscal tissue, which is severe enough to cause the meniscal cartilage to fail and let go. These usually occur from a twisting injury or a blow to the side of the knee that causes the meniscus to be levered against and compressed. A football clipping injury or a fall backwards onto the heel with rotation of the lower leg are common examples of this injury pattern. In a person under 30 years of age this typically requires a fairly violent injury although any age group can sustain a traumatic tear.
Degenerative meniscal tears are best thought of as a failure of the meniscus over time. There is a natural drying-out of the inner centre of the meniscus that can begin in the late 20's and progresses with age. The meniscus becomes less elastic and compliant and as a result may fail with only minimal trauma (such as just getting down into a squat). Sometimes there are no memorable injuries or violent events which can be blamed as the cause of the tear. The association of these tears with ageing makes degenerative tears in a teenager uncommon.
A meniscus can tear in almost any conceivable geometric pattern and in any location. Tears confined to the anterior horn of the cartilage however are unusual. Typically tears begin in the posterior horn and then can extend forward into the middle body and even anterior horn.