Knee Bones: Anatomy and Functions Diagram

The knee is made up of 3 bones: femur, tibia and patella. The femur and tibia form the primary hinge joint, while the patella protects and boost leverage. Your knee supports 80% of your body weight when standing and absorbs impact forces up to 5 times your body weight while running. The tibia bears 85% of the load during weight-bearing activities, while the fibula provides lateral stability. Ligaments and cartilage cushion these bones, preventing injury.

Here’s a breakdown of knee bones, their anatomy, functions, and key roles. Plus, tips on keeping your knee bones healthy and preventing issues.

Knee Bones Anatomy: The 3 Bones of the Knee

The knee is an engineering wonder made up of 3 bones:

• The femur or thigh bone forms the top of the knee and connects to the tibia.
• The tibia or shin bone is the bottom of the knee.
• The patella or kneecap is a shield that protects the knee joint from impacts.

These bones work together for smooth movement.

The knee joint is not just a hinge, it’s a weight bearing structure that supports our body during walking, running and jumping. It’s amazing how these 3 bones work together to allow such a wide range of movement in the knee joints.

Looking at each of these bones will give you insight into their role in knee anatomy and daily activities.

Knee Bones Diagram

Image by brgfx on Freepik

1. Femur: Thigh Bone

The femur or thigh bone is the largest and strongest bone in the human body. This big bone is necessary for us to stand and walk. It can bear up to 30 times our body weight, making it essential for our daily activities.

The anatomy of the femur has a long shaft that supports our body weight and 2 rounded ends that connect to the knee joint. These ends are called the medial femoral condyle and articulate with the tibia to form the knee joint. The femur’s design is for stability and flexibility so we can move freely.

The femur also supports the muscles, tendons and ligaments around the hip and knee. This complex system is what allows us to move smoothly and balance.

Now let’s look at the tibia, a bone that works with the femur to form the knee joint.

2. Tibia: Shin Bone

The tibia or shin bone is the larger and stronger of the 2 bones in the lower leg. It supports the body’s weight so it’s essential for standing and walking. The tibia’s strength and durability is what keeps us upright and mobile.

The medial tibial plateau is the part of the tibia that bears most of the weight load during movement. This area is crucial in weight bearing and impact activities like running and jumping. The tibia’s triangular shape in cross section with 3 borders and surfaces gives it an advantage.

With the femur, the tibia forms the tibiofemoral joint, the main hinge joint of the knee. This joint is for knee flexion and extension so we can do many activities.

Now let’s look at the patella, the bone that shields our knee joint.

3. Patella: Kneecap

The patella or kneecap is the largest sesamoid bone in the body, embedded in the quadriceps femoris tendon. This small but important bone increases the moment arm of the patellar ligament so the quadriceps can extend the knee more efficiently. In short it makes the quadriceps more effective in extending the knee.

The patella is a bony shield for the deeper parts of the knee joint, protecting them from friction and impact. It reduces tendon contact with the femur so wear and tear on the knee structures below is minimized. During knee movement, the patella glides superiorly during extension and inferiorly during flexion, guided by the quadriceps contraction.

Now that we know the patella’s role, let’s look at the articular cartilage and menisci which are essential for the knee joint to move smoothly.

Articular Cartilage and Menisci

Articular cartilage is the smooth, white tissue that covers the ends of the bones where they meet to form joints. In the knee, this cartilage allows smooth movement between the femur, tibia and patella, reducing friction and wear.

The articular surfaces of the knee are the patellofemoral and tibiofemoral joints which are for knee function.

The menisci are 2 crescent shaped pieces of cartilage between the femur and tibia. The medial meniscus is larger and more stable while the lateral meniscus is more variable in shape and size.

These structures act as shock absorbers, spreading the weight across the knee joint and reducing stress on the bones. They also lubricate and nourish the articular cartilage so the medial and lateral menisci remain healthy and functional.

Common injuries to the menisci like tears occur during twisting or pivoting movements. These injuries can affect knee stability and function so it’s clear how important these small but mighty structures are.

Also if you want to locate your knee pain you can check our knee pain diagnosis chart

Cruciate Ligaments

The cruciate ligaments are the ACL and PCL. These ligaments cross each other within the knee, forming a crucial support structure that prevents excessive forward and backward movement of the tibia relative to the femur.

ACL injuries are the most common knee injuries especially in sports that involve cutting and pivoting movements. Symptoms are a popping sound, then pain and swelling. MRI is the imaging modality of choice for these injuries, it’s the best way to see the damage.

Surgical repairs for ligament injuries usually involve arthroscopic surgery, using grafts from the hamstring, patellar tendon or allografts to restore stability. These ligaments show how important they are for knee function and the consequences of the injuries on mobility.

Collateral Ligaments

The medial collateral ligament (MCL) and the lateral collateral ligament (LCL) are for stabilizing the knee against sideways motion.

The MCL connects the femur to the tibia on the inner side of the knee while the LCL connects the femur to the fibula on the outer side. These ligaments prevent side to side movement so the knee remains stable during activities.

Collateral ligament injuries occur from direct blows or excessive stress on the knee. These injuries can affect knee stability and needs proper treatment and rehab to get back to full function.

Tendons and Soft Tissue

The quadriceps tendon connects the quadriceps muscles to the upper part of the patella, it’s crucial for knee extension. Below the patella the patellar tendon (also known as patellar ligament) attaches to the tibia, further movement of the knee.

Soft tissue like the 3 hamstring tendons that cross the back of the knee are part of the knee function.

Injuries to these soft tissue often occur with bone injuries, it shows how connected the knee anatomy is.

Common Knee Injuries Involving Bones

Knee injuries are common especially those involving the bones like the patella. The patella is the most common fractured bone in the knee area, often from significant impact like falls or car accidents. These fractures are painful and debilitating and needs immediate medical attention.

Knee dislocation is less common but can occur from high energy trauma or structural abnormalities. These injuries need surgical intervention to get back to normal alignment and function.

Common knee injuries that requires surgery:

1. Patellar Fractures: From direct trauma to the knee.
2. Knee Dislocations: From high energy impact and can be severe.
3. Ligamentous Tears: Common in sports, affects stability.
4. Meniscal Tears: Common in twisting injuries, affects knee function.

These injuries shows how important the knee anatomy is for health and mobility. Now let’s look at the blood supply and nerve innervation that makes the knee function optimally.

Blood Supply and Nerve Innervation

The knee’s blood supply comes from the popliteal and femoral arteries with contributions from around 10 smaller arteries that form a genicular anastomosis.

These arteries ensures that the knee gets enough blood flow which is important for healing and joint health. The genicular arteries has superior and inferior branches that supplies blood to different parts of the knee joint. This network ensures that all area of the knee is well supplied with oxygen and nutrients.

The knee’s blood supply comes from:

• Popliteal Artery: Main supplier of blood to the knee.
• Femoral Artery: Contributes to knee blood flow.
• Genicular Arteries: Forms a network around the knee for overall blood supply.

This network ensures that all area of the knee is well supplied with oxygen and nutrients which is important for healing and joint health.

The knee joint’s innervation has branches from:

• Femoral Nerve: Main nerve supply of the knee.
• Tibial Nerve: Contributes to knee innervation.
• Common Fibular Nerve: Contributes to knee innervation.
• Posterior Division of the Obturator Nerve: Contributes to knee innervation.
• Saphenous Nerve (branch of the femoral nerve): Supplies sensation to the skin over the medial aspect of the knee. This network of nerves is important for knee function and sensation.

Bottom Line : Summary

As mentioned the femur, tibia and patella is the core structure, supported by ligaments, tendons and soft tissues. The articular cartilage and menisci is for smooth movement and shock absorption, while the cruciate and collateral ligaments is for stability.

Now that we know how each part works together, we can appreciate more the importance of taking care of our knees.

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