How does the knee function?
The knee is a complicated joint that is critical for our ability to walk, our ability to run, or even our ability to simply live pain free. It is composed of 3 bones: the tibia (or shinbone), the femur (or thigh bone), and the patella (or kneecap). In order to ensure that these 3 bones have smooth interactions with each other, they are lined by cartilage. Cartilage is crucial for knee function. It lubricates the joint and creates a smooth surface so that the tibia, femur, and patella can all glide in a synchronized fashion with each other. Without proper cartilage, these three bones can rub directly against each other leading to “wear and tear.” This can affect function of the joint and can be debilitatingly painful.
What is the meniscus?
The menisci play a crucial role in protecting the knee joint. The menisci are two C-shaped shock absorbers that are located between the tibia and femur within the knee joint When viewed as a cross section, they are wedge shaped These shock absorbers are critical to the long term function of the knee. Their wedge shape allows them to create a perfect fit between the round end of the femur and the flat edge of the tibia within the joint. This fit allows for an even distribution of forces and minimizes regions of high contact pressure. The menisci have many more important roles in the knee, but their ability to absorb forces between the thigh bone and shin bone is the most crucial.
How do the menisci work?
The menisci have a unique composition of protein fibers that allow them to absorb forces. They have parallel fibers that expand circumferentially. They also have fibers that intersect these circumferential fibers at a 90-degree angle. Together, this creates a mesh-like honeycomb network. When a patient is walking, their femur presses down on their tibia. The menisci are between the two and will get squeezed as well. When the menisci are being compressed, a portion of the force is pushed outwards away from the knee joint due to this unique protein fiber configuration. By reducing the amount of force that is transmitted from the femur to the tibia, the menisci will protect the cartilage of the knee. Over years and decades, this cumulative protective effect is crucial. It will delay or prevent the onset of severe symptomatic arthritis.