Try something with us. Lock your knees and try to walk. Don’t let them bend!
Pretty dang hard, huh? That’s because the knees are fundamental in facilitating locomotion (what a fun word), a.k.a., any form of movement through space. Whether it's walking, running, swimming, or biking, knees are the crucial link between the agility of your feet and the power of your hips. This essential yet often overlooked connection is at the core of many knee problems. Join us as we look into the anatomy of your knees, focusing on their role in the constant tug-of-war between your feet and hips. Learn why this ongoing battle can make knees vulnerable and how to keep them strong and healthy.
Da Bones of The Knee
What bones make up the knee?
- The femur, a.k.a. your thigh bone, specifically the lower end that meets the knee
- The tibia, a.k.a. the shin bone that really hurts when you don’t see that wood bed frame sticking out
- The patella, a.k.a. your knee joint’s very own helmet
Take a closer look at these bones here:
The first x-ray shows a lateral (side) view of the knee joint. The small, floaty piece to the right—that’s the patella. The bone on top—that’s the femur. The bone on the bottom—that’s the tibia.
Now for a little side tangent we’ll go down since this x-ray is so cool. Bring your attention to the space between the femur and the tibia. What is this space? This is the "joint space," and it's SO important for the health of your knees. Within the joint space is articular cartilage that covers the ends of the femur and the tibia, and the menisci, two crescent-shaped discs that act as shock absorbers and help stabilize the joint. The cartilage and menisci ensure for smooth movement, amongst other things, at the knee. Smooth movement = pain free movement. Since these structures are made of soft tissue, they don’t show up on x-rays, and hence we see space! We’ll dive deeper into this later, so keep reading.
Why should you care about the bones that make up the knee? Well, if you're reading this because you have knee pain, it might not actually stem from the knee itself, but rather from foot/ankle or hip dysfunction. Let's zoom out to explore this concept deeper.
Notice the top bone of the knee in the x-ray above? Follow it up. Where does it go? To the hip! This connection isn’t trivial; it’s a dynamic bridge that influences how forces from our body's core are transmitted to the ground. Now, trace the bottom bone of the knee down. Where does it lead? To the ankle! And this pathway is critical, as it dictates the transfer of ground forces back up through our legs. These shared bones are precisely why the knee often runs into trouble. It's not an autonomous structure; it’s made from extensions of other joints. Yet, the knee is expertly engineered to cope with being the middleman, adeptly balancing the demands placed upon it from both the hip and the foot/ankle, ensuring smooth and efficient movement.
Soft Tissues to the Rescue!
As we touched on before, the knee is cushioned by both articular cartilage and menisci. Other soft tissues that support the knee include ligaments. Take a gander at the pic below.
What do all these soft tissues do?
Articular Cartilage: Smooth, durable tissue that covers the ends of the femur and tibia, as well as the back of the patella. Its slick surface minimizes friction, allowing for effortless joint movement.
Menisci: Two wedge-shaped pieces of fibrocartilage (the medial and lateral meniscus) situated between the femur and tibia. They act as shock absorbers, distribute weight, and stabilize the knee during movement.
Anterior Cruciate Ligament (ACL): Runs diagonally in the middle of the knee, preventing the tibia from sliding out in front of the femur, and providing rotational stability to the knee.
Posterior Cruciate Ligament (PCL): Located at the back of the knee, it prevents the tibia from sliding backward under the femur.
Medial Collateral Ligament (MCL): Provides stability to the inner knee by resisting widening of the joint on the inside.
Lateral Collateral Ligament (LCL): Stabilizes the outer knee, preventing excessive movement in response to force from the inner side of the knee.
The soft tissues within the knee are crucial for absorbing and distributing forces from the foot/ankle and hip. Articular cartilage facilitates smooth joint motion by minimizing friction. Menisci serve as shock absorbers, distributing loads evenly across the knee. Ligaments stabilize the knee, countering imbalances and maintaining joint alignment. This sophisticated system allows the knee to manage stress, ensuring both mobility and stability.
Alignment and posture are key to reducing strain on these soft tissues. The positioning of the femur's top in the acetabulum (hip joint) influences how its bottom articulates with the tibia, affecting knee movement. Proper alignment ensures the cartilage experiences minimal friction, reducing wear and tear. Similarly, the tibia's position on the foot's talus affects its interaction with the femur. Excessive foot and ankle movement can destabilize the tibia, while too little movement results in stiffness, impeding smooth motion. Therefore, maintaining the health of your knee's soft tissues involves addressing feet and hip mobility through practices like Pilates, which focus on holistic movement and alignment.
If you want to learn more about the anatomy of your feet or how the feet affect the kinetic chain, we have blog posts for both! Click here to get nerdy with feet anatomy. Click here to get nerdy with how foot health impacts the kinetic chain.
Back to the knee.
Joint Type Matters
One final anatomical aspect of the knee that we cannot forget is the fact that it’s a synovial joint. A syno-what, you ask?
A synovial joint is a type of joint that is encased in a capsule and filled with synovial fluid, facilitating smooth, lubricated movement between bones. Imagine this as a nourishing water balloon, where the synovial fluid acts like water. This fluid-filled capsule ensures that the articular surfaces within the knee are well-lubricated and nourished, allowing them to move against each other with ease. Just like a water balloon can deform and adjust to pressure without losing its integrity, the synovial joint supports dynamic movement and absorbs impact, all while protecting the bones and soft tissues it encases. This design is fundamental to the knee's ability to perform a wide range of movements smoothly and efficiently.
If your a picture person, check it out:
Why are we so excited about the knee being a synovial joint and why should you care? At Pilates in Common, we’re all about helping people move better, and movement plays a crucial role in the health of synovial joints like the knee. Movement promotes the circulation of synovial fluid, essential for lubricating and nourishing the joint.
The act of moving the knee helps distribute synovial fluid across the articular surfaces, reducing friction and wear. Additionally, it maintains the fluid's viscosity, ensuring effective cushioning and shock absorption.
Regular, moderate exercise stimulates synovial fluid production, enhancing the joint's lubrication and overall cartilage health. This is because physical activity boosts blood flow to the joint area, supplying the necessary nutrients for synovial fluid production and cartilage maintenance.
On the flip side, lack of movement can cause joint stiffening and tissue degradation over time. Without regular activity, synovial fluid circulation decreases, leading to increased friction, wear on the articular surfaces, and a higher risk of joint issues.
In summary, consistent movement is vital for the health of synovial joints like the knee, ensuring effective lubrication, reducing wear and tear, and supporting joint tissue health. Exercises that promote a full range of motion and strength, such as Pilates, are particularly beneficial. Your hip joints are also synovial joints, but that's for another post!
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