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POTH 225: BIOMECHANICS > lecture 5: biomecanics of the knee > Flashcards

lecture 5: biomecanics of the knee Flashcards

1
Q

what are the two articulations in the knee

A

tibiofemoral
patellofemoral

(tibia, patella, femur)

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2
Q

the superior tibiofibular involves what bones

A

tibia
fibular

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3
Q

femur is angled laterally or medially from the vertical

A

inferior side goes in medially

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4
Q

in the femur, the medial and lateral condyles articulate with what

A

the tibia

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5
Q

the patellar surface of the femur articulates with what

A

patella

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6
Q

are there any differences in the femoral condyles

A

yes, diff sizes

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7
Q

true or false: the lateral condyle articulating surface is larger anterior-posterior

A

false, the medial condyle

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8
Q

why is the medial condyle surface larger anterior to posterior

A

largest area = helps distribute the forces

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9
Q

lateral condyle anterior surface extends further anteriorly, why>?

A

prevent lateral patella dislocation

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10
Q

true or false, since the medial condyle extends further anteriorly, it prevents patella discloation

A

false, lateral

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11
Q

which femoral condyle is more curved

A

medial femora condyle

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12
Q

what helps prevental lateral patellar dislocation

A

the fact that the lateral condyle anterior surface extends further anteriorly

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13
Q

in the tibia, which tibial plateau is larger

A

the medial tibial plateau is larger than the lateral plateau

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14
Q

why is the medial tibial plateau larger than the lateral plauteau

A

increased medial loading
helps decrease stress (force/area)

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15
Q

why is there more medial loading on the knee

A

because the ground reaction force is more towards the middle

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16
Q

what are the meniscie

A

fibrocartilage disks

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17
Q

what shape are the menisci

A

wedged shape

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18
Q

where are the menisci located

A

between the femur and tibia

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19
Q

is there blood supply to the menisci

A

some blood supply peripherally
(but there is an avascular cetner)

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20
Q

if you tear the menisci peripherally, can it be repaired

A

possibile beacuse there is some blood supply there

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21
Q

what is the function of the menisci

A

increase contact area between tibia and femur (approximately double the area)

(stress= force/area)

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22
Q

when there is a meniscu tear, why would it be a bad idea to remove it the menisci completely

A

more joint loading and degeneration

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23
Q

what type of joint is the knee

A

modified hinge joint

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24
Q

how many degrees of freedom in the knee (modified hinge joint)

A

2 degrees of freedom

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25
Q

what are the movements possible at the knee joint

A

flexion and extension
medial and lateral rotation
(minimal adduction and abduction)

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26
Q

what is the disagreement about degrees of motion in the knee

A

that there at 6 DOG
(conjuct rotation and translation) but we have no control over these accessry motions

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27
Q

medial and lateal rotation (transverse plane) of the knee happens along what axis

A

sup/inf

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28
Q

flexion and rotation (sagital plane) of the knee happens along what axis

A

medial and lateral axis

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29
Q

adduction and abduction (frontal plane) happens aling what axis

A

arond the ant/post axis

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30
Q

what is the normal range of motion for knee flexion

A

140

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31
Q

what is the normal range of motion for knee extension

A

0

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32
Q

what is the normal range of motion for knee external/lateral rotaiton

A

45

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33
Q

what is the normal range of motion for knee internal/medial

A

30

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34
Q

what is the normal range of motion for knee abduction/adduction

A

a few degrees

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35
Q

what is the knee flexion needed for walking

A

67

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36
Q

what is the knee flexion needed for sit to stand

A

99 (104 in previous example)

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37
Q

what is the knee flexion needed for sit to stand (low chair)

A

105

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38
Q

what is the knee flexion needed for stairs

A

99

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39
Q

what is the knee flexion needed for getting out of bath

A

138

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40
Q

understand the gait saggital knee angle graph

A

.

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41
Q

during heel strike, is the knee angle in extension or flexion

A

in extension

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42
Q

what happens at 20% of gait cycle in terms of the knee angle

A

there is an increase in knee flexiion beacuse we are at fullweight bearing position
in flexion to decrease the impact of the ground reaction force and absorb shock

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43
Q

from 20-40% what happens to the sagital angle of the knee

A

goes back into extension to help clear foot off the ground

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44
Q

what happens to knee angle between 60-100% of gait cycle

A

initially, knee flexion increases because foot is in swing phase and need to clear the gound

from 80-100%, knee goes back into extension to prepare the leg for ground contact

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45
Q

what is the peak knee joint reaction force for level walking

A

3-4 BQ

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46
Q

what is the peak knee joint reaction force for stair climbing

A

5.4

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47
Q

what is the peak knee joint reaction force for lifting

A

2.12

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48
Q

what is the peak knee joint reaction force for jogging

A

12.4 BW

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49
Q

what is the peak knee joint reaction force for squatting

A

7.6 Bw

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50
Q

what requires peak knee joint reaction force of 3-4 BW

A

level walking

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51
Q

what requires peak knee joint reaction force of 5.4 BW

A

stair climbing

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52
Q

what requires peak knee joint reaction force of 2.12 BW

A

lifting

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53
Q

what requires peak knee joint reaction force of 12.4 BW

A

jogging

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54
Q

what requires peak knee joint reaction force of 7.6 BW

A

squatting

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55
Q

during rotation, direciton of intraarticular glide is predictid by what

A

shape of joint surface

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56
Q

if bone with the concave surface moves on the convex surface, the concave articular surface glides where

A

in the same direction as the bone segments roll

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57
Q

if bone with the convex surface moves on the concave surface, the convex articular surface glides where

A

in the direction oppostie of the bone rolling motion

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58
Q

true or false: the knee DOES NOT follow the convex-concave rule!

A

true

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59
Q

during knee flexion (closed kinetic chain), explain the joint surface motion

A

lateral femoral condyle moves posterior with knee flexion
medial femoral condyle movement is less clear

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60
Q

during knee flexion (closed kinetic chain), what is the motion of the femoral condyles

A

lateral femoral condyle moves posterior with knee flexion
medial femoral condyle movement is less clear

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61
Q

during knee flexion (closed kinetic chain), does the lateral femoral condyle move posterior or anterior

A

posterior

62
Q

explain the screw home mechanism (overall)

A

lateral (external) rotation of tibia on femur during extension (open kinetic chain)

medial (internal rotation) of femur on tibia during extension (closed kinetic chain)

63
Q

during knee flexion (closed kinetic chain), what is the motion of the femur

A

femur laterally rotates wrt tibia
posterior roll of femur - contact migrates posterior
lateral femur condyle translates posterior wrt tibia
medial femur condyle moves less than lateral sade

64
Q

during knee extension (closed kinetic chain), what is the motion of the femur

A

femur medially rotates wrt to tibia
anterior roll of femur - cotnact migrates anterior
lateral femur condule translates anterior wrt tibia
medial femur condyle moves less than lateral side

65
Q

during knee flexion (closed kinetic chain), the femur rotates laterally or medially wrt tobia

A

laterally

66
Q

during knee flexion (closed kinetic chain), is there posterior or anterior roll of the femur

A

posterior roll of the femur, contact migrates posterior

67
Q

during knee flexion (closed kinetic chain), how does the lateral femoral condyle move

A

translates posterior wrt tibia

68
Q

during knee flexion (closed kinetic chain), how does the medial femoral condule move

A

moves less than the lateral side

69
Q

during knee extension (closed kinetic chain), the femur rotates laterally or medially wrt tobia

A

medially

70
Q

during knee extension (closed kinetic chain), is there posterior or anterior roll of the femur

A

anterior roll of femur (contact migrates anterior)

71
Q

during knee extension (closed kinetic chain), how does the lateral femoral condyle move

A

translates anterior wrt tibia

72
Q

during knee extension (closed kinetic chain), how does the medial femoral condyle move

A

moves less than the lateral side

73
Q

during Knee flexion (open kinetic chain), explain movement of tibia

A
  • Tibia medially rotates w.r.t. to the femur
  • Posterior roll of tibia- contact migrates posterior
  • Lateral tibia plateau translates anterior w.r.t. femur
  • Medial tibia plateau moves less than lateral side
74
Q

during Knee extension (open kinetic chain), explain movement of tibia

A
  • Tibia laterally rotates w.r.t. to the femur
  • Anterior roll of tibia- contact migrates anterior
  • Lateral tibia plateau translates posterior w.r.t. femur
  • Medial tibia plateau moves less than lateral side
75
Q

during knee flexion (open kinetic chain) does the tibia rotate laterally or medially wrt to the femur

A

tibia medially rotates wrt to the femur

76
Q

during knee extension (open kinetic chain) does the tibia rotate laterally or medially wrt to the femur

A

the tibia laterally rotates wrt to femur

77
Q

during knee flexion, is there anterior or posterior roll of the tibia

A

posterior roll of the tibia (contact migrates posterior)

78
Q

during knee extension, is there anterior or posterior roll of the tibia

A

atnerior roll of the tibia (contact migrates anterior)

79
Q

during knee flexion, what is the movement of the lateral tibia plautea

A

translates anterior wrt femur

80
Q

during knee extension what is the movement of the lateral tibia plautea

A

translates posterior wrt to femur

81
Q

during knee flexion, what is the movement of the medial tibia plautea

A

moves less than lateral side

82
Q

during knee extension, what is the movement of the medial tibia plautea

A

moves less than the lateral side

83
Q

what is axis 1 of the mechanical axis angle

A

center of femoral head to center of knee

84
Q

what is axis 2 of the mechanical axis angle

A

center of ankle to center of knee

85
Q

what is the angle normal angle between axis 1 and 2 for the mechanical axis angle

A

normal is 2 degrees varus

86
Q

explain varus of the knee

A

distal segment (tibia) deviates medially on proximal segment (femur)
smaller than 180

87
Q

in varus of the knee, is the angle greater or less than 180

A

less than

88
Q

explain valgus of the knee

A

distal segment (tibia) deviates laterally on the proximal segment (femur)
greater than 180

89
Q

in valgus of the knee, is the angle greater or less than 180

A

greater than

90
Q

what is knee osteoarthritis

A

deterioration of joint tissue (bone cartilage)

91
Q

which allignment increases the risk of medial compartment knee OA dev and progression

A

varus allignment

92
Q

which allignment increases the risk of lateral compartment knee OA dev and progression

A

valgus allignment

93
Q

varus allignment increases the risk of BLANK compartment knee OA dev and progression

A

medial

94
Q

valgus allignment increases the risk of BLANK compartment knee OA dev and progression

A

lateral

95
Q

why is medial compartment knee OA dev and progression more common

A

because GRF is inclined more medially

96
Q

explain how varus causes more medial loading

A

varus creates a greater moment arm which increases the adduction moment
this wants to pull the medial tibia inwards
this increases medial loading

97
Q

higher adduction loading increases medial or lateral loading

A

medial

98
Q

how do you correct knee allignment

A

High tibial osteotomy

99
Q

to correct limb allignment, what do you have to chagne

A

change the mechanical axis angle (usually less varus)

100
Q

when you are correcting limb alignment and changing the mechanical axis angle, you are usually attempting to get less varus or valgus

A

less varus

101
Q

allighment correction of the knee decreases what

A

medial compartment loading

102
Q

alignment correction of the knee slows what

A

knee OA disease progressions

103
Q

Explain the results of the study of high tibial osteotomy

A

decrease in mechanimal axis angle and knee adduction moment during gait 2 years after high tibial osteotomy

104
Q

medial collateral ligament stabilizes against what force

A

valgus (abductor force)

105
Q

what is more commonly injured, medial or laterall collateral leg

A

medial

106
Q

how is the medial colalteral lig usualy injured

A

knee planted
knee struck on the outside

107
Q

the lateral collateral ligament stabilizes against what force

A

varus (adductor force)

108
Q

true or false; tthe lateral collateral ligament stabilizes against valgus force

A

false, varus

109
Q

explain how the lateral collateral lig is injured

A

less common, usually with multilig injuries

110
Q

what is the function of the anterior cruciate lgi

A

resist anterior glide of tibia (may also resist rotation, varus/valgus)

111
Q

what is the funtcion of the posterior cruciate lig

A

resist posterior glide of tibia, rotation, varus and valgus

112
Q

what is the mecahism for a contact injury of thje acl

A

foot planted, femur driven posterior
rotation

113
Q

what is the mechanism for a non contact acl injury

A

landing, deceleration, pivoting/cuttibg
knee/hip in extension and valgus
quadriceps overload

114
Q

are contact or non contacl acl injuries more common

A

non contact (more common in fems)

115
Q

how can quadriceps overload cause an acl injury

A

pulls tibia anterior (higher anterior shear, pulls tibia forward and strains acl)

116
Q

explain the vulnerable position for the back for acl mechanism of injury

A

forward flexed
rotated oppostie side

117
Q

explain the vulnerable position for the hips for acl mechanism of injury

A

adduction, internal rotation

118
Q

explain the vulnerable position for the knee for acl mechanism of injury

A

less flexed, valgus

119
Q

explain the vulnerable position for the tibial rotation for acl mechanism of injury

A

internal or extenal

120
Q

explain the vulnerable position for the landing patter for acl mechanism of injury

A

one foot out of control or unbalanced

121
Q

there are prevention programs designed to improve dynamic alighment , but did they work ?

A

metaanalysis: fifa 11 reduced injuries by 39% in soccer players

decreased knee valgus moments in female children during double leg jump but not other activiesi (no change in knee angles)

122
Q

what happens to moment arm of the trunk with knee flexion

A

moment arm of the trunk weight increases with increases knee flexion (takes more quad work to balance)

123
Q

since moment arm of the trunk weight increases with increases knee flexion, what happens to the quadfs

A

must increase work to balance

124
Q

when standing starightm the moment arm is where

A

middle of the knee

125
Q

understand slide about closed kinetic chain squatting and the impact on the moment arm of the trunk wwight (and what quads have to do)

A

since moment arm of trunk weight increaes with flexion, this increases the moment.
Quads must create extension moment to counteract body weight (must increase work to balance forces)

126
Q

what happens to moment arm of the ankle weight and leg with knee extension (open kinetic chain)

A

moment arm of ankle weight and leg increases as knee extends, icnreases flexion moment
=more quadriceps work (extension moment to balance)

127
Q

in open kinetic chain, is the moment arm longer in knee flexion or extension

A

knee extension

128
Q

in flexion, moment arm between weight of ankle and knee will icnrease or decrease and what does that do to quads

A

it will decrease therefore quadricep force and work will decrease

129
Q

in full extnesion of knee, what happens with moment arm and quad work

A

there is the longest moment arm between weight or ankle and knees therefore there is an increased flexion moment, the quads must increase force to balance

130
Q

what type of bone is the opatella

A

sesmoid bone

131
Q

where is the patella located

A

knee
imbedded on quad tendon

132
Q

what is the functin of the patella

A

increase the moment arm of the quads tendon (increase effectiveness of quads)
protect quadriceps tendon from excessive frcition from the femur

133
Q

explain the effect of patella on moment arm

A

the patella lengthens the level arm, therefore to do the same moment, the quads will have to work less

134
Q

what are the 2 lines of the q angle

A

line 1: ASIS to patella centre
line 2: tibial tubercle to patella centre

135
Q

what is the Q angle

A

angle between lines 1 and 2

136
Q

what is the normal q angle for men and women

A

13 for men
18 for women

137
Q

what are you at risk for with increased Q angle

A

increased risk of anterior knee pain (patellofemoral pain syndrome) and lateral patella dislocation

138
Q

there is an increased risk of anterior knee pain (patellofemoral pain syndrome) and lateral patella dislocation with an increased or decreased Q angle

A

increased

139
Q

what does the q angle represent

A

lateral pull of quadriceps on patella
(incrase Q angle = incrase latearl pull)

140
Q

increase q angle increases medial or lateral pull

A

lateral pull

141
Q

what is the protection against an icnreased Q angle

A

lateral femoral condyle (larger anterior)
medial extensor retinaculum
vastus medialis

142
Q

how does the patella move during knee flexion

A

patella glides inferior during knee flexion
(more contact between patella and femur)

143
Q

is there more contact between patella and femur during flexion or etension of the knee

A

flexion

144
Q

during full knee extension, there is minimal or maximal contact between patella and femur

A

minimal

145
Q

as patella slides inferior, thjere is an BLANK contact with femur

A

increase

146
Q

does the superior or interior aspect of the patella get more contact points

A

increased contact points as you move superiorly

147
Q

greater knee felxion, the more the patella is pulled where

A

more the patella is pulled towards the femur

148
Q

explain the different in patella joint forces beetween 5 degrees and 70 degreses knee flexion

A

at 5 degrees, the quad is pulling more vertically (less joint reaction force)

at 70 degrees, the quad is pulling more posterioly against the femur and increases the joint raction forces

149
Q

explain the patella joint reaction force during free weight with increases knee felxion angle

A

initially, in full extension, there is low contact between patella and femur

As you increased flexion, there is an increase posterior pull of patella on femur which increases the joint reaction forces

at the end, with increased flexion, the moment arm of the ankle decreases alot therefore decrases the patella joint reaciton forces

150
Q

explain the patella joint reaction force during closed with increases knee felxion angle

A

1) with increasing flexion, there is an increased posterior pull on the patella (increasing patella joint reaction forces)

2) As you squat, body weight moves posteriorly and that icnreases the moment arm and moment
this means an increased force of quads needed to maintain upright which incrases patella joint recation forces

151
Q

be able to interpret patella joint reaction forces

A

POTH 225: BIOMECHANICS (15 decks)

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