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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
The menisci do not withstand ____ but do ___ ____
Compression | but do resist tension
26
Menisci - Horns
open ends | Horns attach to the intercondylar tubercles
27
Menisci - Transverse ligament
Connects the two menisci together anteriorly
28
Menisci - Coronary ligament
Connects the menisci to the tibia underneath - they are attached to the tibia
29
Mensci - Patellomeniscal ligaments
enlargements of the joint capsule
30
Medial meniscus is attached to
C - is attached to the MCL and semimembranosus
31
Lateral meniscus is attached to
O - PCL and popliteus
32
Function of menisci
Semilunar cartilages Stabilize the joint - deepen the articular surfaces Shock absorption - improved congruency of joint surfaces Force distribution within the joint
33
Removal of the menisci would lead to
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
34
Menisci get vascularization from
joint capsule and synovial membrane
35
Role of the meniscus in a normal knee during extension
Path of instantaneous center of rotation (ICOR) Moves post and then ant Moves sup with ext (inf with flex)
36
Knee without menisci - role
Variable ICOR Inc A/P glide Early degeneration of articular cartilage
37
Menisci move/deform ___ with flex
post
38
Menisci move/deform ____ with ext
ant
39
Patella is a
anatomic pulley - friction reduction | Largest sesamoid bone
40
Patella is the ____ congruent joint in the body
Least congruent | Congruent surfaces are large but the amount of contact in diff motions is limited
41
2 things that the patella does
Protects the knee (ant) | Improves the mechanical advantage of the quads
42
Loss of the patella results in
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
Post view of the patella - facets
Lateral facet is larger than the medial facet | Facet angle = 138
44
The more the knee is flexed... (patellar contact)
the farther down the patella is in contact with the condyles of the femur - over the fossa
45
Two structures attached to the patella
Quads and patellar tendon | Muscle will change length so patella follows the tibia
46
With knee extension, the tibia moves
anteriorly and the patella moves more proximal
47
Most congruency of the patella with the articular surface and the groove
around 90 degrees
48
Patellar tendon MA
Max near 45 deg of flex
49
Patella Alta
Patella rides too high up on the femur, patellar groove shallower and can result in knee capsular dislocation in lateral direction
50
Patella Baja
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
Why are you at disadvantage with patella baja?
you arent getting the MA at 45 degrees that it should be so dec effectiveness of quads and limits contact for force distribution
52
Genu Valgum
abnormal angulation of tibia away from the midline | Leg mechanical axis is displaced laterally
53
Genu Valgum - forces
Medial structures - tensile Lateral - compressive Relatively more load on the lateral side btw lateral condyle and lat tibial plateau
54
Genu Varum
Abnormal angulation of tibia toward the midline | Leg mechanical axis is displaced medially
55
Genu Varum - forces
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
Genu Recurvatum
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
Genu Recurvatum - forces
Anterior structures - subject to compression | Posterior structures - subject to tension
58
Genu Recurvatum - excessive...
knee hyperextension Excessive strain on ACL Excessive extension torque in standing Flexors at back of knee are constantly active
59
The Q angle is influenced by
Patellar location Knee joint frontal plane alignment varum/valgum Femoral torsion Tibial torsion
60
Patellar ligament is a continuation of
the tendon of the quadriceps
61
Bowstring effect
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
Chondromalacia
inflammation (softening of the cartilage)
63
Sagittal plane What axis? What movement? Magnitude?
Mediolateral axis Flex = 135 Ext = 5-10
64
Frontal plane What axis? What movement? Magnitude?
Anteroposterior axis Varus/Valgus Hard to measure
65
Transverse plane What axis? What movement? Magnitude?
Vertical at 90 degrees flexion IR = 30 ER = 40 Depends on flexion
66
Joints inside the capsule
Tibiofemoral and patellofemoral
67
Cruciate ligaments are
outside the synovial membrane but inside the joint capsule
68
Fibular Collateral Ligament (LCL)
Lateral femoral epicondyle to fibular head | Resists varus stresses and ER of the tibia
69
LCL is tight in
extension slack in flexion If someone hits you from medial side, this resists tendency to become bow legged in that situation
70
Tibial Collateral Ligament (MCL)
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
MCL is tight in
ext, slack in flexion | ant portion is tight in flexion too
72
Anterior Cruciate Ligament
Ant intercondylar eminence to post part of the medial aspect of the lateral femoral condyle (in the fossa)
73
ACL - 3 bands
anteromedial intermediate posterolateral
74
ACL resists
ant tibial translation hyperextension tibial IR, ER (?)
75
PCL
posterior intercondylar eminence to lateral aspect of medial femoral condyle on medial aspect of ACL
76
PCL - 2 bands
anterolateral | posteromedial
77
PCL resists
post tibial translation, flexion, and tibial IR (?), ER (?)
78
PCL - more tight with flex, is this the case throughout the range though?
Yes until 90 degrees of flexion and then importance decreases Post tibial translation with transected PCL - no diff at 150
79
Arcuate popliteal ligament
reinforces posterolateral capsule helps LCL resists varus stress
80
Oblique popliteal ligament
sup lat to inf medial reinforces posteromedial capsule resists valgus stress and limits ER
81
Medial and lateral retinaculum
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
IT Band
Consistently tight | Attachments at knee
83
IT Band Attachments at knee
Iliopatellar band - causes lateral pull on patella Lateral tibial tubercle - assists ACL in resisting ant translation of tibia on femur Resists varus stress
84
TFL action changes with
joint position knee ext - contributes to ext knee flex - contributes to flex
85
Knee Functional Stability
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
Open Chain Arthrokinematics
``` Swing phase Tibia on femur distal on proximal Concave on convex Roll and glide in same direction ```
87
Closed Chain Arthrokinematics
``` Stance phase Femur on tibia proximal on distal Convex on concave Roll and glide in opposite direction ```
88
Closed kinetic chain - flexion
Roll post | Glide ant
89
Closed kinetic chain - extension
Roll ant | Glide post
90
Screw home mechanism
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
Screw home mechanism - when the knee is bending with gait the tibia
rotates medially with respect to the femur
92
Causes of the screw home mechanism
Bony asymmetry | ligament tension
93
Open chain - during terminal extension
ER of tibia on femur
94
Closed chain - during terminal extension
IR of femur on tibia
95
Closed packed position
extension
96
Loose packed position
25 degrees flexion
97
Knee joint flexors
``` Biceps femoris Semimem and semitend Gracilis Sartorius TFL at more than 45 degrees popliteus gastroc plantaris ```
98
Knee joint extensors
``` rectus femoris vastus lateralis vastus medialis vastus intermedius TFL less than 30 degrees ```
99
Knee joint IR
Semiten and semimem Sartorius Gracilis Popliteus
100
Knee joint ER
biceps femoris
101
Squat vs leg extension | Leg extension
trains quad in extension range where external torque is high because of MA Good for stability and safety
102
Squat vs leg extension | Squat
trains quad in flexion range
103
Quad mechanics with knee flexion angle - ability to produce force depends on
ability to produce force depends on length and ma

Semester 2 FS Exam 8 (1 decks)

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