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Biomechanics IV > Exam 2 lecture: Knee > Flashcards

Exam 2 lecture: Knee Flashcards

1
Q

what is the largest joint in the body?

A

tibiofemoral

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2
Q

name the 3 joints that make up the knee joint complex

A

tibiofemoral, patellofemoral, proximal tibiofibular joint

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3
Q

what type of joint is the tibiofemoral joint? (simple, compound, complex)

A

complex

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4
Q

what type of joint is the patellofemoral joint? (simple, compound, complex)

A

compound

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5
Q

what type of joint is the proximal tibiofibular joint? (simple, compound, complex)

A

simple

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6
Q

t or f: the tibiofemoral jt is bicondylar w/2 menisci

A

true

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7
Q

what joint causes the most patient complaints?

A

patellofemoral

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8
Q

t or f: the knee is the most common site of permanent injury in the lower limb.

A

true

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9
Q

where are the largest forces in the knee?

A 
tibiofemoral joint (posterior compartment)
patellofemoral joint (anterior compartment)
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10
Q

what separates the femoral condyles?

A

fossa

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11
Q

why does the knee have menisci?

A

b/c it needs a variable socket

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12
Q

t or f: the femoral condyles are egg-shaped: large posteriorly and small anteriorly.

A

false. the femoral condyles are egg shaped, but large anteriorly and smaller posteriorly

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13
Q

why do the femoral condyles have divergent axes?

A

may increase stability of joint

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14
Q

what is the significance of the posterior angulation of the femoral condyles?

A

lots of flexion, not much extension

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15
Q

which femoral condyle is larger? why?

A

medial b/c of conjoint rotation

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16
Q

what muscle inserts on the medial epicondyle?

A

medial hamstring

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17
Q

t or f: the medial femoral condyle is more oblique than the lateral femoral condyle (longer from A-P)

A

true

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18
Q

what is anteversion?

A

femoral torsion

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19
Q

what is the normal range for femoral torsion?

A

10-20˚

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20
Q

what is an anteverted femur (degrees)?

A

> 20˚

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21
Q

what is a common compensation for anteverted femur?

A

genu valgum

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22
Q

what is a retroverted femur (degrees)?

A

<10˚

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23
Q

what is a common compensation for retroverted femur?

A

genu varum

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24
Q

what is a squinting patella?

A

patella faces medially

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25
Q

what happens if squinting patella is uncompensated?

A

genu varum and toe in

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26
Q

what are the possible compensations for squinting patella?

A

genu valgum
increased external tibial torsion
foot flare

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27
Q

t or f: squinting patella + increased tibial torsion –> feet more parallel w/line of progression

A

true

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28
Q

are the tibial condyles concave or convex?

A

neither; they are flat

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29
Q

what are the functions of the tibial spines?

A

attachment points for ACL and menisci

stabilizing effect

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30
Q

are the tibial articular facets concave or convex?

A

neither, they are flat.

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31
Q

t or f: tibial facets are perfectly round

A

false. the medial side is larger than the lateral side (egg shaped)

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32
Q

what is the significance of the posterior angulation of the tibial condyles?

A

more flexion ROM

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33
Q

what happens if the tibial condyles are broken?

A

heals w/less angulation –> more hyperextension, less flexion

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34
Q

what attaches to gerdy’s tubercle?

A

ITB

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35
Q

what type of cartilage lines the patellar surface of the femur?

A

hyaline

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36
Q

what is the main function of the patella?

A

increase the angular pull of the quads

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37
Q

which way does the patellar apex point?

A

downward

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38
Q

which patellar facet is larger?

A

lateral

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39
Q

why does the patella have the thickest cartilage in the body?

A

highest compression and shear forces in the body

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40
Q

t or f: there is more cartilage in the tibiofemoral jt than in the patellofemoral jt.

A

false. there is more cartilage in the patellofemoral jt than the tibiofemoral jt.

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41
Q

what is the Q angle?

A

represents the pull of the quads; angle is taken from 2 intersecting lines:
ASIS –> center of patella
center of patella –> tibial tuberosity

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42
Q

what is the normal Q angle range?

A

5-15˚

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43
Q

t or f: the Q angle is highly dependent on gender

A

false. the Q angle is more determined by height than gender

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44
Q

what is the patellofemoral ratio?

A

distance from patella to tibia : height of patella

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45
Q

what patellofemoral ratio is patella baja? what does patella baja mean?

A

<0.8; patella too low

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46
Q

what patellofemoral ratio is patella alta? what does patella alta mean?

A

> 1.2; patella too high

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47
Q

what is the name for a too-large patella?

A

patella magna

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48
Q

what is the name for a too-small patella?

A

patella parva

49
Q

what are the problems with patella alta?

A

more likely to dislocate, unstable

50
Q

what are the problems with patella baja?

A

more stable, can cause abnormal wear and tear

51
Q

what is the ideal patellofemoral ratio?

A

1 +/- .2

52
Q

what happens to the Q angle during medial/internal rotation of the tibia?

A

decreases

53
Q

what happens to the Q angle during lateral/external rotation of the tibia?

A

increases

54
Q

what is the effect of foot flare on the Q angle

A

increases the Q angle

55
Q

name some situations in which the patella is less stable

A 
knee is extended
VMO is weak/stretched medial retinaculum
genu valgum
vastus lateralis or ITB too tight
patella is too small or facel angle is too flat
small lateral lip or shallow groove
patella alta
externally rotated tibia or increased foot flart
excessive foot pronation
56
Q

name some situations in which the patella is more stable

A 
knee flexed
strong VMO
genu varum
normal patella, patellar groove, large lateral lip
normal or lower patellar position 
normal or under pronation
57
Q

t or f: compression forces on the patella increase w/extension

A

false. compression forces increase w/flexion

58
Q

when is there the most force on the patella?

A

when jumping

59
Q

which direction does the patella glide during flexion?

A

inferior and posterior

60
Q

t or f: the patella increases extensor leverage more when it is less flexed.

A

true

61
Q

t or f: the quadriceps force increases as knees flex more (i.e. during squatting)

A

true

62
Q

VMO or VL responds faster to tension?

A

VMO (reverse in patellofemoral pain syndrome)

63
Q

why are the anterior compartment ligaments not true ligaments?

A

b/c they are attached by tendon expansions

64
Q

t or f: a pt with quad rupture cannot extend the knee.

A

false. pt with quad rupture can still extend the knee b/c of retinacular attachments

65
Q

MR tear + valgus sprain + patellar dislocation = ?

A

lateral patellar instability

66
Q

t or f: medial and lateral retinaculae have less intense forces on them during flexion/extension activities than the central tendinous band

A

true.

67
Q

what does the ITB blend with?

A

lateral retinaculum

68
Q

what are the parts of the ITB?

A

smaller patellar band

larger tibial band

69
Q

what happens when ITB is tight?

A

rubs on lateral femoral condyle

pulls on patella

70
Q

what are synovial plica?

A

remnant of 3 embryonic cavities, usually small and asymptomatic

71
Q

what are the common complications of synovial plica?

A

recurrent snapping and pain

72
Q

what are the functions of the menisci?

A

deepen socket –> stability and congruency
flexible socket –> accomodate egg shpaed femoral condyles
accomodate slide –> decreased shear stress
decrease compression on articular surfaces (force directed to periphery)
reduce wear and tear

73
Q

how much compressive load does each meniscus transmit to the periphery?

A

lateral: 70%
medial: 50%

74
Q

what shape is the medial meniscus?

A

C shaped

75
Q

what shape is the lateral meniscus?

A

O shaped

76
Q

which meniscus is more often injured?

A

medial meniscus

77
Q

which meniscus is more mobile?

A

lateral meniscus

78
Q

why is the medial meniscus less mobile?

A

b/c of attachment to medial collateral lig.

79
Q

which way to the menisci (and synovial fluid) slide when the knee flexes?

A

posterior

80
Q

where is stress increased during deep squats?

A

posterior horns

81
Q

which way do the menisci (and synovial fluid) slide when the knee extends?

A

anterior

82
Q

when is there more pressure on the menisci?

A

at full extension (but less focal)

83
Q

t or f: menisci rotate w/tibia

A

false. the menisci rotate w/the femur

84
Q

which way does each meniscus move during internal rotation?

A

medial: anterior
lateral: posterior

85
Q

what is the retreating meniscus test

A

lateral meniscus should move posteriorly during internal rotation

86
Q

which meniscus takes more pressure during internal rotation?

A

medial

87
Q

which meniscus takes more pressure during external rotation?

A

lateral

88
Q

what are the effects of varus stress on the menisci?

A

pinches medial meniscus

tractions lateral meniscus thru coronary ligs.

89
Q

what are the effects of valgus stress on the menisci?

A

pinches lateral meniscus

tractions medial meniscus thru medial collateral lig and coronary ligs

90
Q

which type of stress is more common (valgus v. varus)? why?

A

valgus b/c lateral leg is more accessible (e.g. via tackle, etc.)

91
Q

t or f: there is potential for injury to the menisci w/any movement

A

true

92
Q

which are the most common mechanisms of injury to the menisci?

A

deep flexion
hyper-extension
external rotation
valgus stress

93
Q

what is the old unhappy triad?

A

medial meniscus, ACL, MCL

94
Q

what is the new unhappy triad?

A

medial meniscus, ACL, LCL

95
Q

why are menisci poor healers?

A

not well vascularized

96
Q

how much of the menisci are vascularized?

A

outer 1/3

97
Q

how do the menisci get nutrients?

A

from synovial fluid

98
Q

what type of innervation do the mensci have and where?

A

pain and proprioception @ junction w/deep capsule

99
Q

what are the effects of aging on the menisci?

A

decreased vascularization
increased wear and tear
increased fragility

100
Q

name the collateral ligs

A

medial (tibial) CL
lateral (fibular) CL
poplitiofibular lig (post. to LCL)

101
Q

which collateral lig is larger?

A

medial

102
Q

what are the attachments for the LCL?

A

lateral femoral condyle, fibular head

103
Q

what type of stress does the LCL mostly resist?

A

varus

104
Q

what are the attachments for the MCL?

A

medial femoral epicondyle, medial tibial condyle and shaft

105
Q

what type of stress does the MCL mosty resist?

A

valgus

106
Q

t or f: medial rotation –> increased stress of collateral ligs.

A

false. medial rotation –> decreased stress on collateral ligs

107
Q

why is the decreased stress on the collateral ligs during medial rotation significant?

A

allows conjoint medial rotation

108
Q

what action of the foot would be affected if the collaterals limited medial rotation?

A

pronation (decreased)

109
Q

does lateral rotation increase or decrease tension on the collateral ligs?

A

increase

110
Q

what structures make up the posteromedial capsular complex?

A

posterior part of medial collateral lig.
semimembranosis tendon & tendon expansion
oblique popliteal lig.

111
Q

what is the function of the posteromedial capsular complex?

A 
resist hyperextension
resist valgus stress
resist anterior translation
resist extremes of lateral tibial rotation
protect ACL
112
Q

what structures make up the posterolateral capsular complex?

A 
LCL
poplitiofibular lig
arcuate lig
biceps femoris tendon and tendon expansion
popliteus
113
Q

what motions does the posterolateral capsular complex resist?

A

anterior translation
hyperextension
varus stress
extremes of medial and lateral rotation

114
Q

why does the LCL become lax when the knee flexes?

A

so it doesnt limit medial tibial rotation and foot pronation

115
Q

what lig is tense during knee flexion?

A

PFL

116
Q

t or f: PFL is more resistant to anterior translation stability than LCL

A

true

117
Q

what is the order of ligamentous failure when the leg is extended?

A

LCL, PFL, popliteus & arcuate lig.

118
Q

what is the most common cause of hemarthrosis?

A

ACL tear

Biomechanics IV (5 decks)

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