Biomechanics of the Knee Joint
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Questions and Answers

What type of joint is the knee classified as?

  • Hinge joint
  • Pivot joint
  • Bi-condylar synovial joint (correct)
  • Ball and socket joint

Which bones are primarily involved in the knee joint?

  • Humerus, scapula, clavicle
  • Pelvis, coxal bone, femur
  • Femur, tibia, patella (correct)
  • Fibula, ulna, radius

Which articulations are included within the knee joint capsule?

  • Tibiofemoral and patellofemoral (correct)
  • Interphalangeal and metacarpophalangeal
  • Proximal tibiofibular and distal tibiofibular
  • Humeroulnar and radiohumeral

What is the main function of the articular cartilage in the knee joint?

<p>To decrease friction between articulating bones (B)</p> Signup and view all the answers

Which part of the knee joint is considered the weight-bearing joint?

<p>Tibiofemoral joint (A)</p> Signup and view all the answers

What separates the medial and lateral condyles of the femur?

<p>Intercondylar notch (D)</p> Signup and view all the answers

The tibial plateau is best described as having what kind of shape?

<p>Asymmetrical and relatively flat (D)</p> Signup and view all the answers

What role does the proximal tibiofibular joint play in relation to the knee?

<p>It provides attachment for muscles and ligaments (A)</p> Signup and view all the answers

Which tibial plateau bears most of the load during stance when the knee is extended?

<p>Medial tibial plateau (C)</p> Signup and view all the answers

What is the approximate surface area relationship between the medial and lateral tibial plateaus?

<p>The medial plateau is 60% larger (D)</p> Signup and view all the answers

How do the menisci contribute to the tibiofemoral joint?

<p>By distributing loads and absorbing forces (D)</p> Signup and view all the answers

What percentage of the total load can the menisci bear?

<p>45% (B)</p> Signup and view all the answers

What happens to patellofemoral compression during knee flexion?

<p>It increases due to greater force components (B)</p> Signup and view all the answers

What factor increases the compressive force at the patellofemoral joint during stair climbing?

<p>Increased quadriceps tension (D)</p> Signup and view all the answers

What is recommended for minimizing knee forces during training?

<p>Training within the 0–50° knee flexion range (D)</p> Signup and view all the answers

What is a consequence of a meniscectomy regarding joint health?

<p>Increased risk of degenerative conditions (D)</p> Signup and view all the answers

What role does the PCL play when the knee is flexed between 75-90 degrees?

<p>It resists posterior translation and shearing forces. (B)</p> Signup and view all the answers

Which muscle plays an important role in stabilizing the knee from posterior shearing forces when the PCL is damaged?

<p>Popliteus (A)</p> Signup and view all the answers

Which bursa is located between the quadriceps femoris and the femur?

<p>Suprapatellar bursa (D)</p> Signup and view all the answers

Which muscles are primarily responsible for medial rotation at the knee?

<p>Semimembranosus, semitendinosus, sartorius, gracilis, popliteus (C)</p> Signup and view all the answers

What happens to the PCL during hamstring contraction in a PCL deficient person?

<p>It destabilizes the knee joint. (A)</p> Signup and view all the answers

How does the PCL best resist medial tibial rotation?

<p>At 90 degrees of knee flexion. (A)</p> Signup and view all the answers

What condition describes the knee's position when it locks in a closed kinematic chain?

<p>Occurs at 30-degree flexion. (D)</p> Signup and view all the answers

Which bursa is located between the semimembranosus muscle and the medial head of the gastrocnemius?

<p>Semimembranosus bursa (C)</p> Signup and view all the answers

What is the primary function of the menisci in the knee?

<p>To enhance stability and distribute loads (A)</p> Signup and view all the answers

How do the menisci contribute to shock absorption in the knee?

<p>By deepening the articulating depressions of the tibial plateaus (C)</p> Signup and view all the answers

Which statement about the medial and lateral menisci is correct?

<p>The medial meniscus has firmer attachments than the lateral meniscus (D)</p> Signup and view all the answers

What role does the synovial membrane play in the knee joint?

<p>It produces synovial fluid for lubrication (B)</p> Signup and view all the answers

What factor contributes to the menisci's ability to resist compression?

<p>Their internal structure being designed for compression (D)</p> Signup and view all the answers

Which of the following is NOT a component of the knee joint's stability?

<p>The synovial fluid (C)</p> Signup and view all the answers

During which activity can compressive loads through the knee reach up to 3-4 times body weight?

<p>Running (A)</p> Signup and view all the answers

What happens to the knee's stability in a flexed position compared to an extended position?

<p>It becomes less stable (C)</p> Signup and view all the answers

What is the primary function of the ACL?

<p>To resist anterior shearing forces on the knee (C)</p> Signup and view all the answers

Which bundle of the ACL is under the most tension at approximately 10-15 degrees of knee flexion?

<p>Anteromedial bundle (AMB) (D)</p> Signup and view all the answers

What is a key factor contributing to the strength of the PCL compared to the ACL?

<p>Its larger cross-sectional area (C)</p> Signup and view all the answers

At approximately what degree of knee flexion is neither the AMB nor the PLB of the ACL taut?

<p>30 degrees (D)</p> Signup and view all the answers

What movement is commonly associated with ACL injuries?

<p>Twisting movements (B)</p> Signup and view all the answers

Which statement accurately describes the PCL's bundles of fibers?

<p>The anterolateral bundle is larger and stronger than the posteromedial bundle. (D)</p> Signup and view all the answers

Which ligament is theorized to provide the most effective rotary stability of the knee?

<p>Posterolateral bundle (PLB) of the ACL (D)</p> Signup and view all the answers

How does the PCL's anatomy compare to that of the ACL?

<p>The PCL has a larger surface area and is less frequently injured. (A)</p> Signup and view all the answers

What is the primary role of the intercondylar tubercles in the knee?

<p>To aid in knee extension stability (C)</p> Signup and view all the answers

Which structure is NOT considered a part of the dynamic restraints of the knee?

<p>Menisci (B)</p> Signup and view all the answers

How do the medial and lateral menisci differ in shape?

<p>Medial meniscus is 'C' shaped; lateral meniscus is 'O' shaped (B)</p> Signup and view all the answers

What type of joint is the tibiofemoral joint classified as?

<p>Modified hinge joint (A)</p> Signup and view all the answers

What is the significance of the sloping of the tibia shaft?

<p>To facilitate flexion of the femoral condyles (C)</p> Signup and view all the answers

What is the primary attachment point of the medial meniscus?

<p>Medial collateral ligament (D)</p> Signup and view all the answers

How do the femoral condyles interact with the menisci?

<p>The menisci are flat inferiorly and concave superiorly (C)</p> Signup and view all the answers

What contributes to the overall instability of the tibiofemoral joint?

<p>The convex shape of the tibial plateaus (A)</p> Signup and view all the answers

Flashcards

Menisci and Proprioception

The outer portion of each meniscus has nerve endings, providing information about the knee's position and movement.

Meniscus Function

The menisci deepen the tibial plateau and distribute load throughout the knee, reducing stress.

Meniscus Internal Structure

The medial two-thirds of the meniscus resists compression due to its strong internal structure.

Meniscus Stability

The menisci help coordinate knee motion and stabilize the joint.

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Meniscus Wear Reduction

The menisci spread out axial loads, reducing wear on the articular cartilage.

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Meniscus Mobility

The medial meniscus is more firmly attached to the joint capsule and MCL, making it less mobile than the lateral meniscus.

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Joint Capsule Structure

The joint capsule protects and stabilizes the knee, with a thicker outer layer and a thinner inner layer.

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Synovial Membrane Function

The synovial membrane inside the capsule produces synovial fluid, which lubricates the knee.

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Tibial Plateau Shape & Slope

The medial tibial plateau is longer anteroposteriorly than the lateral plateau, and the proximal tibia's diameter is greater posteriorly than the shaft. This slope helps the femur flex on the tibia.

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Intercondylar Tubercles

The two rounded ends of the tibia (tibial condyles) are separated by two bony bumps called intercondylar tubercles. These tubercles are rough and help lock the knee in an extended position.

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Tibiofemoral Joint Type & Stability

The tibiofemoral joint is a hinge joint that allows for six different types of movements. Despite this, the joint itself is not inherently stable.

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Patellofemoral Joint

The patellofemoral joint is where the kneecap (patella) meets the thigh bone (femur). The patella is a key part of the knee's extensor mechanism, with its movement determined by the position of the tibia and femur.

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Mensical Attachments & Thickness

The menisci are attached to the tibia by the coronary ligaments and joint capsule. They are thickest on the edges and thin towards the center.

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Medial Meniscus Connection & Blood Supply

The medial meniscus is connected to the medial collateral ligament. Both menisci have a rich blood supply and nerve network.

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Menisci Role in Stability

The menisci are crucial for stability of the knee joint. They help distribute forces and prevent excessive movement of the femur on the tibia.

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What are the bones involved in the knee joint?

The knee joint is a complex structure formed by the femur, tibia, patella, and numerous ligaments and muscles.

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What are the primary movements allowed by the knee joint?

The knee joint allows for flexion and extension (bending and straightening) and limited medial and lateral rotation.

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What type of cartilage is found in the knee joint?

Articular cartilage, a smooth, hard substance, covers the articulating surfaces of the femur, tibia, and patella, minimizing friction during movement.

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What is the primary weight-bearing joint in the knee?

The weight-bearing joint in the knee is the tibiofemoral joint, formed by the articulation of the femur's condyles with the tibia's plateau.

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What is the second important joint in the knee?

The patellofemoral joint, formed by the articulation of the patella with the femur's groove, also plays a role in knee function.

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Describe the intercondylar notch and femoral sulcus.

The intercondylar notch is the space between the two condyles of the femur, while the femoral sulcus (patella groove) is a shallow groove on the anterior surface of the femur that helps to stabilize the patella.

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Describe the tibia's condyles.

The tibia's two condyles, known as the tibial plateau, provide a relatively flat surface for articulation with the femur.

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What is the role of the fibula in the knee?

Although not directly part of the knee joint, the fibula, a bone adjacent to the tibia, provides an attachment point for important muscles and ligaments.

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Tibial Plateau Load Distribution

The medial tibial plateau supports the majority of weight during standing, while the lateral plateau handles less weight during swinging.

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Why Medial Tibial Plateau is Larger?

The medial tibial plateau is larger than the lateral plateau, reducing stress on the joint.

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Cartilage Thickness Difference

The medial tibial cartilage is thicker than the lateral cartilage, acting as a shock absorber.

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Meniscus Force Absorption

Menisci help absorb forces at the knee, taking up a significant portion of the load.

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Meniscus Damage and OA

Damage to the meniscus can lead to osteoarthritis due to increased wear and tear on the joint.

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Patellofemoral Joint Force During Activity

The force at the patellofemoral joint during walking is half of body weight, increasing significantly during activities like stair climbing.

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Patellofemoral Force and Knee Flexion

As the knee bends, the compressive force at the patellofemoral joint increases due to the increased component of force and the need for more quadriceps tension to maintain stability.

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PCL and Posterior Translation

The PCL is most effective at resisting forces pulling the tibia backwards (posterior translation) when the knee is bent (flexed), even though the tibia can move backwards the most at 75-90 degrees of flexion.

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PCL and Knee Stability

The PCL also helps keep the knee from twisting (rotating) and from bending inwards or outwards (valgus/varus forces).

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PCL and Tibia Rotation

The PCL is better at preventing the tibia from rotating inwards (medial rotation) when the knee is bent at 90 degrees than when it's straight (extended). However, it isn't good at preventing the tibia from rotating outwards (lateral rotation).

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What is a Bursa?

A bursa is a fluid-filled pouch that cushions and reduces friction where structures move against each other, like in a joint.

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Suprapatellar Bursa Location

The suprapatellar bursa is located between the quadriceps muscle (the front thigh muscle) and the femur (your thigh bone).

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Prepatellar Bursa Location

The prepatellar bursa is located between the tip of the kneecap (patella) and your skin.

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Infrapatellar Bursa Location

The infrapatellar bursa is located in two parts, a deep one between the shinbone (tibia) and the patellar ligament, and a superficial one between the patellar ligament and your skin.

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Semimembranosus Bursa Location

The semimembranosus bursa is located at the back of the knee joint, between the semimembranosus muscle and the medial head of the gastrocnemius muscle.

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What is the ACL?

This ligament, named for its shape, connects the front of the tibia to the back of the femur, helping control the knee's forwards movement.

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How is the ACL divided?

The ACL has two bundles that work together - the anteromedial bundle (AMB) and the posterolateral bundle (PLB). These bundles tighten and loosen as the knee bends, controlling forward movement.

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How do the ACL bundles work during knee motion?

When the knee is nearly fully extended, the PLB is taut (tight), resisting forward movement. As the knee bends, the PLB relaxes and the AMB tightens, continuing to control forward movement.

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What is the main role of the ACL?

The ACL is essential for controlling how much the tibia moves forward or backward in relation to the femur. It also contributes to overall knee stability.

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What is the PCL?

This ligament, located behind the ACL, connects from the back of the tibia to the front of the femur, limiting backward movement of the tibia.

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How is the PCL structured and how does it work?

The PCL is bigger than the ACL and has two bundles as well. When the knee is nearly extended, the PMB is taut, while the ALB is slack; as the knee bends, the ALB tightens and the PMB relaxes.

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How does the strength of the PCL compare to the ACL?

The PCL has a larger cross-sectional area than the ACL and is generally considered to be stronger, making it less prone to injury.

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What's the main function of the PCL?

The PCL's primary role is to resist backward movement of the tibia relative to the femur. It acts as a crucial stabilizing ligament for the knee joint.

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Study Notes

Biomechanics of the Knee Joint

  • The knee is a large, complex synovial joint, crucial for locomotion and weight-bearing.
  • It's a bi-condylar joint allowing flexion, extension, and slight medial/lateral rotation.
  • The knee includes three articulations within the joint capsule: tibiofemoral (weight-bearing), and patellofemoral joints.
  • The proximal tibiofibular joint, though not directly part of the knee, influences knee motion.

Articulating Surfaces

  • The femur, tibia, and patella articulate via cartilage-covered surfaces.
  • Articular cartilage minimizes friction.
  • Tibia's medial and lateral condyles articulate with the femur's corresponding condyles to form the tibiofemoral joint.
  • The femur's anterior and distal aspect articulates with the patella to form the patellofemoral joint.
  • The fibula, running alongside the tibia, provides attachment points for ligaments and muscles.
  • The femur's distal aspect creates the proximal articulating surface, with two condyles (medial and lateral).
  • There's an intercondylar notch and patellar groove for the patella.

Tibiofemoral Joint

  • A modified hinge joint, presenting six degrees of freedom.
  • Joint stability comes from the joint capsule, ligaments, and menisci alongside the dynamic restraints of muscles.

Patellofemoral Joint

  • The patella articulates with the femoral condyles.
  • Patella tracks within the femoral groove.
  • The static and dynamic relationships of the tibia and femur affect patellar tracking.

Menisci

  • Semilunar cartilages that cushion and stabilize the knee by aligning the articulating surfaces.
  • Concave superiorly, flat inferiorly, fitting within the intercondylar notch of the tibia.
  • Medial and lateral menisci differ in shape and attachment.
  • Connected to each other through a transverse ligament, anchored to the tibia (mostly peripherally).

Joint Capsule

  • Thick fibrous layer externally, thinner internally.
  • Contains synovial membrane, which creates synovial fluid for lubrication.
  • Includes infrapatellar fat pad and bursa as cushions.

Ligaments

  • Critical structures providing knee stability.
  • ACL, PCL, MCL, and LCL are crucial in resisting various forces and stresses.
  • Location and orientation of ligaments determine how they resist knee dislocation.

Knee Movements

  • Flexion and extension are primary movements.
  • Muscles (e.g., quadriceps femoris for extension, hamstrings for flexion) control these actions.

Knee Loads

  • Primarily weight-bearing during activities like walking and running.
  • Compressive forces are significant, exceeding body weight during activities like stair climbing.

Pathologic Conditions

  • Excessive genu valgum (knock-knees) and genu varum (bowlegs) are common abnormal knee forms.
  • Genu recarvatum (hyperextension) results in abnormal angles.

Knee Axis

  • Assessing knee alignment involves identifying landmarks and using these to establish mechanical and anatomical axes.
  • Important in analyzing and treating knee misalignment conditions.

Q Angle

  • Measurement of angle between quadriceps muscles and patellar tendon.
  • It shows the dynamic instability of patella. Larger values are associated with higher likelihood of knee pain/issues.

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Biomechanics of Knee Joint PDF

Description

Explore the anatomy and functions of the knee joint in this quiz. Learn about its complex structure, including the tibiofemoral and patellofemoral joints. Assess your understanding of the articulating surfaces and their roles in movement.

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