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  • Writer's pictureHiromi N

The Knee

The power lies on the thigh and the control of the movement directions lies on the foot.

The knee joint connects the upper and the lower leg. The femur receives the weight of the torso through the pelvis directly and the weight transmits through the knee joint to the lower leg and through the ankle joint to the foot.

There are strong ligaments, cartilages and muscles support the movements at the knee joint. And of course, the function of this joint is integrated the movement from above (hip) and the below (ankle) joints.

To begin with, if you simply look at the bone structure, it’s a little bit easier to manage the movements of the leg.

The shape of the lower end of the femur is round, and the top end of the tibia is flat. But the semilunar shape of menisci resolves this bad fit of two bones and the femur can glide on the tibia head efficiently.

This structure, and be able to visualize the femur is gliding on top of the tibia helps to connect both the upper and the lower leg bones in the movement.

It’s not a split movement at the knee joint, it’s always the femur weight or direction of the movement is transmitted and connect to the tibia and the fibula (through the top plate of the tibia), whether the feet is on the ground or not. Even though the rotation of the femur is added to the movement and the movement gets a little more complicated, the connection between the femur and the tibia is applied the same. When this connection is lost, you’re most likely grip the joints of above (the hip) and the below (the ankle).

Simply put it, for just looking at the skeleton at the knee joint, the femur is always sitting on top of the tibia, even the intension of the movement coming from the bottom end (the foot), the connection of the upper and the lower leg remains the same.

When the knee is flexed, the movement looks like the knee is moving forward (both the femur and the tibia are moving pointing forward), but if you move with awareness of the femur is moving on top of the tibia and the tibia is transmitting the weight through the ankle and to the foot, the connection of the flexing motion doesn't exit at the knee joint and it will ground you to the foot.

And just a bit more to share, how the ligaments and the cartilages are designed to support the knee joint is amazing. (I don't mention the muscles now..)

This is explained very well in the book "Body³" by Thomas Myers. I love the way he explains, it helps me to understand a complicated anatomy.

Here is some quick notes from his book about some names and functions of ligaments and cartilages at the knee.

The medial collateral ligament supports inside of the knee by running vertically from the femur to the tibia, it's preventing the femur and the joint from collapsing medially. The lateral collateral ligament supports out side of the knee attached from the femur to the fibula, it's preventing the femur and the joint from collapsing laterally. Both ligaments are further supported by muscles that run outside of them and prevent abduction and adduction of the knee, and permit only a very small transverse motion.

Inside the knee joints are the two cruciate ligaments. It's complicated, but if you summarize, they prevent the knee from hyperextending very far beyond a straight knee, and they act in concert to keep the surface of the femur from rolling or sliding off the knee in all its various positions.

Inside the joint, on either side of the cruciates lie the semilunar cartilages, or menisci, it's like a cushioned plate to fit rounded ends of the femur and the flat top of the tibia.

And so on..

The next post, I would like to share further more about the knee functions!

Image is from POCKET Anatomy & Physiology by Shirley A. Jones

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