Knee Biomechanics Flashcards
What type of joint is the tibiofemoral joint?
Double condyloid
The tibiofemoral joint prevents motion in what plane?
Frontal
The tibiofemoral joint has how many degrees of freedom?
2 degrees of freedom
(T/F) Is the medial tibial plateau larger than the lateral?
YES: 50% larger (oval and long)
Articular cartilage 3x thicker than
lateral
The Medial & lateral tibial plateau slope in which direction?
Slope posteroinferiorly
What are the main functions of the menisci?
- Increase stability by deepening
tibial plateau - Decreases friction by 20%
- Increases contact area by 70%
- Enhances proprioception via
mechanoreceptors - Attenuates forces
The Medial Meniscus is what shape?
C-Shaped
The Lateral Meniscus is what shape?
O-Shaped
Where is the medial meniscus thickest?
Posteriorly
Where is the lateral meniscus thickest?
Uniform thickness
What major structure is firmly attached to the medial meniscus?
MCL
Menisci transmit what percent of
imposed load at knee?
50-60%
Shock absorption capability
is reduced by what percent with complete menisectomy?
20%
The menisci are initially well vascularized but recede to the periphery by what age?
11 years old
The MCL prevents which motion?
Abduction (Valgus)
(T/F) Adduction or abduction is determined by the movement of the distal extremity (tibia)
TRUE
The LCL prevents which motion?
Adduction (varus stress)
The MCL assists in restraining which tibial motion?
Anterior tibial translation
When are ALL the MCL fibers most taut?
Extension
The MCL anterior fibers are taut in which motion?
Mid-range knee flexion
The MCL posterior fibers are on slack in which motion?
Mid-range knee flexion
(T/F) The LCL has an attachment to the joint capsule
FALSE
When are the LCL fibers most taut?
Extension
The LCL helps restrict what motion other than varus?
IR/ER
How many bundles are there in a typical ACL?
3
What is the origin and insertion of the ACL?
Anterior aspect of tibial to posterior aspect of LFC
Average ACL length and width?
33mm Length / 11mm width
What motion does the ACL restrain?
Anterior tibial translation
Which muscle group may help restrain anterior tibial translation?
Hamstrings
Primary function of the PCL?
Prevents posterior translation of tibia on femur
(T/F) The PCL is frequently injured
FALSE
Which ligament prevents anterior translation of the FEMUR?
PCL
Which ligament prevents posterior translation of the FEMUR?
ACL
Which part of the menisci has the greatest healing potential?
Periphery (Red-Red Zone)
What degree of an angle would be considered Genu Valgum?
<165°
What degree of an angle would be considered Genu Varum?
> 180°
Genu valgum can lead to increased pressure on which compartment of the knee?
increased lateral
compressive forces
Genu Varum can lead to increased pressure on which compartment of the knee?
increase medial
compressive forces
Average Q-Angle for males?
10-14°
Average Q-Angle for females?
15-17°
Genu recurvatum is characterized by excessive…?
extension
Decreased CKC dorsiflexion would lead to?
Decreased knee flexion
Decreased CKC plantar flexion would lead to?
Decreased Knee extension
What is the minimum amount of knee flexion required to ambulate?
60° - 70°
Describe the screw home mechanism during open chain extension and flexion
Extension: Tibial ER
Flexion: Tibial IR
Describe the screw home mechanism during closed chain extension and flexion
Extension: Femur ER
Flexion: Femur IR
Roll/Glide mechanics during open chain extension?
Concave on FIXED convex
Tibia rolls and glides anteriorly
Roll/Glide mechanics during open chain flexion?
Concave on FIXED convex
Tibia rolls and glides posteriorly
Roll/Glide mechanics during closed chain extension?
Convex on FIXED concave
Femur rolls anterior / glides posterior
Roll/Glide mechanics during closed chain flexion?
Convex on FIXED concave
Femur rolls posterior / glides anterior
The posterior surface of the patella is covered by which type of cartilage?
Posterior surface is covered with thick hyaline cartilage
The medial facet of the patellofemoral Joint is positioned?
Flat to slightly convex
The lateral facet of the patellofemoral Joint is positioned?
longer than medial
The “odd” facet of the patellofemoral joint is positioned?
medial angle
The 1st consistent patellofemoral contact is between?
10° - 20° flexion
By 90° all aspects of facets have made contact with exception of?
Odd facet
The greatest PF compression force is at what degree of flexion?
90°
What are the Transverse stabilizers leading to Patellofemoral Joint Stability?
Med/lat retinaculum
VMO/VL
MPFL
What are the Longitudinal stabilizers leading to Patellofemoral Joint Stability?
Quad tendon
Patellar tendon
The MCL and LCL, to a lesser extent, resists?
External rotation
3 parts of the unhappy triad?
ACL, MCL, Medial meniscus
