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Semester 2 FS Exam 8 > Knee Biomechanics > Flashcards

Knee Biomechanics Flashcards

1
Q

The knee joint is the ____ and the ____ ____ joint

A

Largest and the most complex joint

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2
Q

Knee joint - mobility

A

No bony stops to mobility - increase potential risk of injury

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3
Q

Knee joint provides mobility for

A

the foot in space

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4
Q

Knee joint - articulations

A

Two distinct articulations contained w/in a single joint capsule: tibiofemoral and patellofemoral

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5
Q

Knee joint - net joint forces in the knee with:
Normal gait
Running/Stair climbing
Single leg landing bball

A

2-3X BW
5-6X BW
10X BW

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6
Q

Knee joint bones

A

Femur
Tibia
Patella
Fibula - included because of attachments that cross the knee joint like biceps femoris, IT band, and LCL

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7
Q

Mechanical axis

A

Connects the hip joint to knee joint
Line of action from hip joint center to knee joint center
Shape of it defines the stresses that are experienced
Tendency to bend with compressive medially and tension laterally

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8
Q

Typical mechanical axis angle

A

3 degrees

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9
Q

Anatomical axis

A

Lateral to mechanical

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10
Q

Typical anatomical axis angle

A

6 degrees

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11
Q

Mechanical and Anatomical angle difference

The bigger the diff…

A

the larger the forces experienced from each surface

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12
Q

The larger the mechanical and anatomical angles, the..

A

more stresses that are experienced

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13
Q

Femoral Condyles - which is longer

A

Medial condyle is longer so will tilt laterally when placed on a flat surface

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14
Q

Patellar groove - more pronounced on which side

A

lateral side - it is more ant than the medial side too

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15
Q

Lateral condyle of the femur is

A

more in line with the shaft so the medial condyle will experience more load

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16
Q

Patellar surface

A

saddle shaped groove

lateral patellar surface is longer

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17
Q

Patella experiences forces that tend to shift it

A

laterally but the lateral patellar surface being longer prevents it from going laterally

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18
Q

Femoral Condyles - Con___

A

Convex

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19
Q

Convexity of femoral condyles on frontal plane

A

small - not a remarkable difference

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20
Q

Convexity of femoral condyles on sagittal plane

A

large, convexity is no consistent
Ant part = larger diameter
Larger diameter = more stability = dec stresses

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21
Q

Convexity of femoral condyles on sagittal plane - ant part vs post part

A

Ant part = larger = extension
Post part = smaller = flexion
MCL and LCL stretched in ext - tight ligaments = more stability in extension

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22
Q

Tibial Articular Surfaces - Plateus

A

Asymmetric
Medial condyle is 50% larger, 3x thicker cartilage
CONCAVE - are flat but concavity comes from the menisci
Because of the mechanical axis there is more force on the medial side and this is good

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23
Q

Femur/tibia articular surface fitting - congruency is best

A

in extension position because articular surfaces of the tibia are flat

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24
Q

Menisci - made up of what type of cartialge

A

Fibrocartilage - more collagen

Arrangement of the collagen is in a circular fashion with layers in the menisci

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25
Q

The menisci do not withstand ____ but do ___ ____

A

Compression

but do resist tension

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26
Q

Menisci - Horns

A

open ends

Horns attach to the intercondylar tubercles

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27
Q

Menisci - Transverse ligament

A

Connects the two menisci together anteriorly

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28
Q

Menisci - Coronary ligament

A

Connects the menisci to the tibia underneath - they are attached to the tibia

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29
Q

Mensci - Patellomeniscal ligaments

A

enlargements of the joint capsule

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30
Q

Medial meniscus is attached to

A

C - is attached to the MCL and semimembranosus

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31
Q

Lateral meniscus is attached to

A

O - PCL and popliteus

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32
Q

Function of menisci

A

Semilunar cartilages
Stabilize the joint - deepen the articular surfaces
Shock absorption - improved congruency of joint surfaces
Force distribution within the joint

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33
Q

Removal of the menisci would lead to

A

Dec the contact area by 50%
Inc 20% of the intrajoint coefficient of friction - Menisci help synovial fluid move so without it you have more friction and potential to lose cartilage becomes more severe

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34
Q

Menisci get vascularization from

A

joint capsule and synovial membrane

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35
Q

Role of the meniscus in a normal knee during extension

A

Path of instantaneous center of rotation (ICOR)
Moves post and then ant
Moves sup with ext (inf with flex)

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36
Q

Knee without menisci - role

A

Variable ICOR
Inc A/P glide
Early degeneration of articular cartilage

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37
Q

Menisci move/deform ___ with flex

A

post

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38
Q

Menisci move/deform ____ with ext

A

ant

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39
Q

Patella is a

A

anatomic pulley - friction reduction

Largest sesamoid bone

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40
Q

Patella is the ____ congruent joint in the body

A

Least congruent

Congruent surfaces are large but the amount of contact in diff motions is limited

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41
Q

2 things that the patella does

A

Protects the knee (ant)

Improves the mechanical advantage of the quads

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42
Q

Loss of the patella results in

A

18-20 % loss of motion
48-50 % loss of effectiveness in extension
Smaller ma
Quads are working at longer length with patella than w/o

43
Q

Post view of the patella - facets

A

Lateral facet is larger than the medial facet

Facet angle = 138

44
Q

The more the knee is flexed… (patellar contact)

A

the farther down the patella is in contact with the condyles of the femur - over the fossa

45
Q

Two structures attached to the patella

A

Quads and patellar tendon

Muscle will change length so patella follows the tibia

46
Q

With knee extension, the tibia moves

A

anteriorly and the patella moves more proximal

47
Q

Most congruency of the patella with the articular surface and the groove

A

around 90 degrees

48
Q

Patellar tendon MA

A

Max near 45 deg of flex

49
Q

Patella Alta

A

Patella rides too high up on the femur, patellar groove shallower and can result in knee capsular dislocation in lateral direction

50
Q

Patella Baja

A

Patella rides too low down on the femur due to patellar tendon shortening after surgery or injury and this puts the system at a disadvantage

51
Q

Why are you at disadvantage with patella baja?

A

you arent getting the MA at 45 degrees that it should be so dec effectiveness of quads and limits contact for force distribution

52
Q

Genu Valgum

A

abnormal angulation of tibia away from the midline

Leg mechanical axis is displaced laterally

53
Q

Genu Valgum - forces

A

Medial structures - tensile
Lateral - compressive
Relatively more load on the lateral side btw lateral condyle and lat tibial plateau

54
Q

Genu Varum

A

Abnormal angulation of tibia toward the midline

Leg mechanical axis is displaced medially

55
Q

Genu Varum - forces

A

medial structures - compressive stress
lateral structures - tensile stress
Typically more load on medial side and now with this even more load on medial side - lateral structures like LCL under constant tension

56
Q

Genu Recurvatum

A

Abnormal angulation of tibia anteriorly - tibia is tilted almost post so tibial plateau is not flat and most load is experienced at the ant tibia
Leg mechanical axis is displaced anteriorly

57
Q

Genu Recurvatum - forces

A

Anterior structures - subject to compression

Posterior structures - subject to tension

58
Q

Genu Recurvatum - excessive…

A

knee hyperextension
Excessive strain on ACL
Excessive extension torque in standing
Flexors at back of knee are constantly active

59
Q

The Q angle is influenced by

A

Patellar location
Knee joint frontal plane alignment varum/valgum
Femoral torsion
Tibial torsion

60
Q

Patellar ligament is a continuation of

A

the tendon of the quadriceps

61
Q

Bowstring effect

A

Effect of Q angle to pull laterally
Draws the patella laterally causing chondromalacia in response to chronic stress
So the larger groove on lateral side is good to prevent this

62
Q

Chondromalacia

A

inflammation (softening of the cartilage)

63
Q

Sagittal plane
What axis?
What movement?
Magnitude?

A

Mediolateral axis
Flex = 135
Ext = 5-10

64
Q

Frontal plane
What axis?
What movement?
Magnitude?

A

Anteroposterior axis
Varus/Valgus
Hard to measure

65
Q

Transverse plane
What axis?
What movement?
Magnitude?

A

Vertical at 90 degrees flexion
IR = 30
ER = 40
Depends on flexion

66
Q

Joints inside the capsule

A

Tibiofemoral and patellofemoral

67
Q

Cruciate ligaments are

A

outside the synovial membrane but inside the joint capsule

68
Q

Fibular Collateral Ligament (LCL)

A

Lateral femoral epicondyle to fibular head

Resists varus stresses and ER of the tibia

69
Q

LCL is tight in

A

extension
slack in flexion
If someone hits you from medial side, this resists tendency to become bow legged in that situation

70
Q

Tibial Collateral Ligament (MCL)

A

medial femoral epicondyle to tibia
resists valgus stress, ER/IR and and translation of tibia
Connects capsule and medial meniscus (so rupture would impact med meniscus)

71
Q

MCL is tight in

A

ext, slack in flexion

ant portion is tight in flexion too

72
Q

Anterior Cruciate Ligament

A

Ant intercondylar eminence to post part of the medial aspect of the lateral femoral condyle (in the fossa)

73
Q

ACL - 3 bands

A

anteromedial
intermediate
posterolateral

74
Q

ACL resists

A

ant tibial translation
hyperextension
tibial IR, ER (?)

75
Q

PCL

A

posterior intercondylar eminence to lateral aspect of medial femoral condyle on medial aspect of ACL

76
Q

PCL - 2 bands

A

anterolateral

posteromedial

77
Q

PCL resists

A

post tibial translation, flexion, and tibial IR (?), ER (?)

78
Q

PCL - more tight with flex, is this the case throughout the range though?

A

Yes until 90 degrees of flexion and then importance decreases
Post tibial translation with transected PCL - no diff at 150

79
Q

Arcuate popliteal ligament

A

reinforces posterolateral capsule
helps LCL
resists varus stress

80
Q

Oblique popliteal ligament

A

sup lat to inf medial
reinforces posteromedial capsule
resists valgus stress and limits ER

81
Q

Medial and lateral retinaculum

A

Often associated of pathomechanics at knee
Can be injured with high resistance forces at quads and twisting forces at the knee
Dont have good MA but help control movement of patella med and lat with tracking

82
Q

IT Band

A

Consistently tight

Attachments at knee

83
Q

IT Band Attachments at knee

A

Iliopatellar band - causes lateral pull on patella
Lateral tibial tubercle - assists ACL in resisting ant translation of tibia on femur
Resists varus stress

84
Q

TFL action changes with

A

joint position
knee ext - contributes to ext
knee flex - contributes to flex

85
Q

Knee Functional Stability

A
  1. No bony stops in motion
  2. Joint geometry change of menisci (1st) - resist tension
  3. Passive restraint from ligaments (2nd)
  4. Active muscles (3rd)
  5. Compressive load - more stability
86
Q

Open Chain Arthrokinematics

A 
Swing phase
Tibia on femur
distal on proximal
Concave on convex
Roll and glide in same direction
87
Q

Closed Chain Arthrokinematics

A 
Stance phase
Femur on tibia
proximal on distal
Convex on concave
Roll and glide in opposite direction
88
Q

Closed kinetic chain - flexion

A

Roll post

Glide ant

89
Q

Closed kinetic chain - extension

A

Roll ant

Glide post

90
Q

Screw home mechanism

A

when we walk we have about 15 degrees of rotation and those 15 degrees happen during last 30 degrees of extension and mostly in the last 5

91
Q

Screw home mechanism - when the knee is bending with gait the tibia

A

rotates medially with respect to the femur

92
Q

Causes of the screw home mechanism

A

Bony asymmetry

ligament tension

93
Q

Open chain - during terminal extension

A

ER of tibia on femur

94
Q

Closed chain - during terminal extension

A

IR of femur on tibia

95
Q

Closed packed position

A

extension

96
Q

Loose packed position

A

25 degrees flexion

97
Q

Knee joint flexors

A 
Biceps femoris
Semimem and semitend
Gracilis
Sartorius
TFL at more than 45 degrees
popliteus 
gastroc
plantaris
98
Q

Knee joint extensors

A 
rectus femoris
vastus lateralis 
vastus medialis
vastus intermedius 
TFL less than 30 degrees
99
Q

Knee joint IR

A

Semiten and semimem
Sartorius
Gracilis
Popliteus

100
Q

Knee joint ER

A

biceps femoris

101
Q

Squat vs leg extension

Leg extension

A

trains quad in extension range where external torque is high because of MA
Good for stability and safety

102
Q

Squat vs leg extension

Squat

A

trains quad in flexion range

103
Q

Quad mechanics with knee flexion angle - ability to produce force depends on

A

ability to produce force depends on length and ma

Semester 2 FS Exam 8 (1 decks)

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