I’ve become acquainted with the cartilaginous tissue in the knee for a couple decades now. The menisci as I have know it, and has commonly been accepted, has one primary purpose - shock absorption. Just like having soft inserts in your shoes to absorb some of the impact from walking, the menisci act in a similar fashion to absorb the shock and disperse the load from the ground reaction forces.
As more research engages and more information is unveiled, our thoughts of how we look at the wonderful world of the meniscus - anatomy, function, surgical procedures, rehabilitative theories, and preventative methods, may all change. One such change that I’ve been exposed to is the function of this tissue. Let’s dive into this a little bit more.
Here’s the commonly acceptance responsibilities of the menisci:
Shock absorption (cushion and padding)
Load transmission (softens and evens out the load)
Here’s what more recent biomechanics research is suggesting:
Lateral Meniscus
Adds stability to the joint
When scoping out the lateral meniscus, recall that it is thicker with more depth to it versus its counterpart. It’s kind of like swimming in the “adult” pool versus the “kiddie” pool. The “adult” pool may be 5 ft, but that’s definitely much deeper than the 1 ft pool that barely hugs around your ankles. If someone tried to push you over, I think it’d be a lot easier to push you off balance in the “kiddie” pool knowing that there is less water resistance countering the force. The “adult” pool contains more water which adds that external barrier to help keep your body upright in place. Similarly, the lateral meniscus has more depth to it, which means the femoral condyles have more stability within the confines of its external meniscal barrier.
Protects condylar rocking especially during the screw-home mechanism
Due to anatomical construct, as you fully extend your knee, your tibia will externally rotate at end range, “screwing” the knee into place. As you bend the knee out of full extension, the lateral femoral condyle rocks laterally and twists to “unscrew” itself. Thankfully due to it being thicker, the lateral meniscus provides more protection and acts as a barrier so that the condyles don’t rub against surrounding tissues. It’s like keeping the rail guards up when learning how to bowl. The rails make sure you bowling ball isn’t swerving too far right or too far left, but straight forward toward the right direction. The lateral meniscus ensures that you keep your condyle directed on the correct path.
Medial Meniscus
Prevents shearing at the joint
When admiring the medial meniscus, recall that the it is wider expanding all around more than its counterpart. This anatomical construct is advantageous as it readily accepts the larger medial femoral condyle and directs the path of the screw-home mechanism. As well, this cartilaginous configuration actually acts similarly to the ACL whereas it prevents and protects agains shear stresses (e.g. anterior translation). Instead of having the leash on to restrain a dog from running around in backyard (ACL), you can also move the surround fence inward so there’s less room for the dog to run within (medial meniscus).
So there you have it! Like I mentioned earlier, I never really thought about the meniscus like this before. I was always taught that the menisci were cartilaginous shock absorbers - the “cushions” in the knees. Apparently, labeling it as that may make you discredit its additional importance in your evaluation methods and rehabilitation techniques. It’s knowing these little conceptual changes that can help you stand out from the rest of the pack!
Change your mindset … Change your perspective … life is much better when you have an
outlook that creates opportunity.
Thanks for being curious and taking the time to read this! Hope it added value to your life and equips you to become better than you were yesterday!
Dr. Joe Jaime, DC, DACBSP®, ATC, CSCS®, FRC®ms, CES
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