32 Questions
What is the primary function of the structure that increases the area of contact between the patellar tendon and the femur?
To reduce patellofemoral joint contact stress
What is the shape of the medial meniscus?
C-shape
What is the primary source of nutrition for the internal part of the meniscus?
Diffusion of synovial fluid
What is the percentage of the meniscal body that is vascularized after 50 years of age?
Only the periphery
What is the purpose of the transverse ligament in the menisci?
To connect the medial and lateral menisci
What is the primary function of the menisci?
To reduce friction between the femur and tibia
What is necessary for the process of fluid diffusion to support meniscal nutrition?
Intermittent loading of the meniscus by weight-bearing or muscular contractions
What is the difference between the medial and lateral menisci in terms of movement?
The medial meniscus is less movable than the lateral meniscus
Which part of the meniscus is capable of inflammation, repair, and remodeling after a tearing injury in adults?
Peripheral vascularized region
What is one of the primary functions of the menisci in the knee joint?
To reduce friction between joint segments
What is the Q-angle formed by?
The line of force of the quadriceps and the line connecting the tibial tuberosity to the midpoint of the patella
Why do females tend to have a larger Q-angle than males?
Due to a wider pelvis and increased femoral anteversion
What is the position of maximum stability of the knee joint?
Maximum extension with maximum lateral rotation
What occurs during the final 5° of knee extension in the automatic or locking mechanism of the knee?
Lateral rotation of the tibia
What contributes to the obligatory rotational motion of the knee during the final 5° of extension?
Increasing tension in the knee joint ligaments
What is the position of minimum stability of the knee joint?
Maximum flexion with maximum lateral rotation
What is the effect of genu valgum on the weight-bearing line?
It shifts the weight-bearing line onto the lateral compartment
What is the consequence of genu valgum or genu varum on the articular cartilage?
It increases the risk of damage and erosion of the articular cartilage
What is the function of the patella in the patellofemoral joint?
It reduces the friction between the patella and the femur
What is the result of the patella's action on the quadriceps tendon?
It increases the angle of pull of the quadriceps tendon on the tibia
What is the effect of the patella on the quadriceps muscles' divergent tension?
It centralizes the divergent tension from the quadriceps muscles
What percentage of improvement in mechanical advantage does the patella provide to the quadriceps muscles?
50%
What is the shape of the patella?
Triangular
What is the location of the articulation of the patellofemoral joint?
Between the patella and the trochlear groove
What are the two distinct articulations located within a single joint capsule in the knee complex?
Tibiofemoral and patellofemoral joints
What is the primary function of the tibiofemoral joint?
Modified hinge joint with some lateral and rotational motions
What is the direction of the anatomical axis of the femur?
Obliquely directed, inferiorly and medially from proximal to distal end
What is the normal angle formed by the femoral and tibial longitudinal axes at the knee joint?
180° to 185°
What is the condition characterized by a medial tibiofemoral angle greater than 185°?
Genu valgum
What is the effect of genu valgum and genu varum on the knee joint?
They alter the compressive and tensile stresses on the medial and lateral compartments
What are the two condyloid joints that function together primarily as a modified hinge joint?
Medial and lateral condyles of the tibia and femur
What is the direction of the anatomical axis of the tibia?
Vertically directed
Study Notes
Knee Joint
- The knee joint consists of two distinct articulations: the tibiofemoral joint and the patellofemoral joint, both located within a single joint capsule.
- The tibiofemoral joint is a modified hinge joint that allows for some lateral and rotational motions.
Menisci
- The medial and lateral menisci are fibrocartilaginous discs connected anteriorly by the transverse ligament.
- They are attached to the intercondylar region of the tibia by anterior and posterior horns.
- The medial meniscus is C-shaped, firmly attached, and less movable, making it more liable to tears.
- The lateral meniscus is O-shaped, easily adapted for sudden twisting movements, and less liable to injury.
Blood Supply of Menisci
- The internal part of the menisci is avascular.
- The peripheral part is supplied by capillaries located in the joint capsule and synovial region.
- During the first year of life, blood vessels are contained throughout the meniscal body.
- After weight-bearing is initiated, vascularity begins to diminish, and only the outer 25% to 33% is vascularized.
Nutrition of Menisci
- The peripheral portion obtains its nutrition through blood vessels.
- The central portion relies on the diffusion of synovial fluid.
- Intermittent loading of the meniscus by weight-bearing or muscular contractions is necessary for fluid diffusion.
Function of Menisci
- Distribute weight-bearing forces, reducing compressive stress.
- Stabilize the joint during motion by increasing congruence.
- Reduce friction between joint segments.
- Act as shock absorbers.
- Fill the space between the femoral and tibial condyles, preventing the posterior capsule from being compromised.
Q-Angle
- The Q-angle is formed by the line of force of the quadriceps and the line connecting the tibial tuberosity with the midpoint of the patella.
- The angle is 15.8° in females and 11.2° in males due to a wider female pelvis, increased femoral anteversion, and relative knee valgus.
Stability of the Knee Joint
- The closed-packed position of maximum stability occurs at maximum extension with maximum lateral rotation.
- The loose-packed position of minimum stability occurs at flexion.
- The automatic or locking mechanism of the knee joint involves lateral rotation of the tibia during the final 5° of extension, contributing to obligatory rotational motion.
This quiz covers the functions of menisci in the human body, including weight distribution, joint stabilization, and shock absorption. It also touches on the repair and remodeling of meniscal tears in adults.
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