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Analysis of Movement > Knee > Flashcards

Knee Flashcards

1
Q

T/F: The knee is a bi-compartmental joint.

A

false, it’s tri-compartmental

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2
Q

Knee joint stability is dependent on what?

A

passive restraint structural integrity (strength of ligaments)

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3
Q

How many planes of motion does the knee move through?

A

2: sagittal and horizontal planes

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4
Q

What does the longitudinal axis of LE tell you? What’s a normal angle?

A

How straight up and down the leg is at the knee: 175 deg

- normally less than 180 since the angle of inclination makes the femur go in slightly (slight natural genu valgus)

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5
Q

With a mechanical axis of 150 deg, what does that tell you about the knee?

A

there’s a genu valgus at the knee: axis is less than 175

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6
Q

What would a genu varus do to the longitudinal axis value?

A

make it >170

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7
Q

What degree classifies a genu recurvatum?

A

> 10 degrees of hyperextension in the knee

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8
Q

What’s an example of a secondary passive-restraint knee stabilizer?

A

posterior capsule

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9
Q

Where is internal joint fluid pressure greatest in the knee?

A

at end ranges (is the least in slight flexion)

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10
Q

What is the position of comfort for the knee?

A

30 degrees flexion

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11
Q

What structures help make up the posterior capsule of the knee?

A

retinaculum comes from…

  • vastus lateralis and medialis
  • IT band
  • popliteal oblique ligament
  • arcuate oblique ligament
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12
Q

T/F: The tibiofemoral joint is inherently stable.

A

false- inherently unstable due to incongruent articular surfaces, leading to many knee injuries

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13
Q

What helps increase the articular congruency in the knee?

A

fibrocartilaginous menisci make tibial surface concave instead of flat; triples the tibiofemoral joint contact area

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14
Q

What do the medial and lateral menisci look like? What are they anchored by?

A

medial = lunar shape
lateral = C-shape
- anchored by the posterior horns

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15
Q

What is a tear of the posterior horns in the knee called? What can this lead to?

A
  • bucket-handle tear, which is found in the inner-zone

* this can lead to unanchored menisci, = knee instability

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16
Q

If we didn’t have menisci, how much larger would the compressive forces be on our body?

A

200x larger, causing bone degeneration (osteoarthritis)

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17
Q

What is the primary function of the menisci? What else does it do? (4)

A

primary = to reduce tibiofemoral joint compression
- also does proprioception, joint stabilization/congruency, arthrokinematic guidance, and articular cartilage lubrication

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18
Q

Why is it so bad to tear the inner zone meniscus?

A

b/c it’s avascular and unlikely to heal; also nothing really anchoring menisci

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19
Q

Which is better, a peripheral tear or inner zone tear of the meniscus?

A

peripheral b/c it has a good blood supply

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20
Q

During what actions is the tibiofemoral joint most compressed?

A
  • 4x compression during stairs

* 2.5-3x compression during walking

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21
Q

Weight bearing causes the menisci to wear down. Where does this occur?

A

on the periphery

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22
Q

What meniscus is more likely to tear? Why?

A
  • medial is more likely to tear b/c it’s attached to MCL and doesn’t move as well
  • LCL isn’t attached to the lateral meniscus due to the popliteal ligament, so it’s more moveable
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23
Q

How many degrees of freedom do we get at the tibiofemoral joint?

A

2: flex/extend and IR/ER

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24
Q

What ROM do we get for KE and KF?

A 
KE = 0-10 degrees hyperextension, common in females
KF = 130-150 degrees
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25
Q

Why can we not get an exact measurement with a goniometer when measuring KE or KF? What landmark do we use to estimate?

A
  • The ML axis of rotation migrates as we move through motion, following the condyle curves
  • since the axis moves, this alters the moment arm of the muscles, so we have to just estimate the axis at the LATERAL EPICONDYLE
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26
Q

At what knee position do we get maximal IR and ER? Which do we get more of?

A
  • when knee is flexed to 90 = max rotation

- get 2x more ER than IR (40-45 deg total)

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27
Q

What landmark do we use to measure rotation of the knee, and what’s it relative to?

A

tibial tuberosity either pointing out or pointing in, relative to femur (foot will also be pointing either in or out usually)

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28
Q

Describe the arthrokinematics of open chain knee extension. What happens with the menisci during this?

A

tibia on femur = concave on convex

  • rolls and slides anterior
  • menisci are pulled anterior also via quads
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29
Q

Describe arthrokinematics of closed-chain knee extension.

A

femur on tibia = convex on concave

- roll anterior, slide posterior

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30
Q

Describe the arthrokinematics of the knee in a downward squat.

A

femur on tibia = convex on concave

- posterior roll, anterior slide

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31
Q

What is the screw-home mechanism? What 4 things allow this to occur?

A

screw-home = last 30 deg of KE need rotation to occur
- this is possible via:

  1. popliteus muscle to unlock
  2. medial condyle more anterior than lateral
  3. lateral pull of quad
  4. passive tension in ACL
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32
Q

To lock the knee, what needs to occur? in open and closed chain

A

open chain lock = tibia ER

closed chain lock = femur IR

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33
Q

What unlocks the knee? How does it do this?

A

popliteus either:

  • open chain unlocks = brings tibia into IR
  • closed chain unlocks = pulls femur out to ER
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34
Q

How can you tear the ACL? (via what extreme motions)

A

via hyperextension and ER

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35
Q

T/F: The knee externally rotates slightly to unlock.

A

false, knee slightly internally rotates to unlock

- but this can be either through IR of tibia or ER of femur, depending on what’s fixed

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36
Q

T/F: Knee must be flexed to maximize independent IR/ER.

A

true

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37
Q

T/F: Menisci get deformed with femur on tibia rotation.

A

true, due to compression over time

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38
Q

T/F: You can get some rotation in full KE.

A

false, none at all. Need knee flexion

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39
Q

How are menisci stabilized?

A

by the posterior horns and their connecting muscles (popliteus and semimembranosis)

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40
Q

What ligament(s) primary function is to restrain frontal plane motion?

A

LCL/MCL

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41
Q

Where is MCL stressed the most?

A

in its DEEP fibers with valgus stress (vs superficial fibers)
- these deep fibers blend with the medial meniscus

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42
Q

T/F: MCL and LCL both restrain IR/ER.

A

true

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43
Q

When are the MCL and LCL both taut?

A

in knee extension

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44
Q

What ligament(s) give multiplanar stability to the knee and guide it’s natural kinematics?

A

ACL/PCL

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45
Q

What kind of receptors do the ACL and PCL have a lot of? What is this for?

A

ACL/PCL have lots of mechanoreceptors, giving proprioception to the knee about where it is in space

46
Q

What regulates muscle contraction force?

A

the mechanoreceptors in the ACL/PCL; can limit muscle force

47
Q

T/F: ACL and PCL both limit rotation.

A

true

48
Q

What kind of rehab, besides strengthening, is essential for ACL/PCL tears and why?

A

neuromuscular rehab is SO important b/c you’ve not only lost stability , but also the mechanoreceptors that tell the knee where it is in space

  • without this, it’s difficult to control muscle force when needed, and the ligaments can tear again
  • tell a pt to reposition their knee (like you showed them) with their eyes closed -> they struggle with this
49
Q

At what degree does the tibia begin to anteriorly slide in KE?

A

last 50-60 degrees of KE; roll first

50
Q

What limits posterior translation of the femur?

A

ACL

51
Q

What is the agonist to the ACL?

A

hamstrings b/c help limit tibial anterior translation

52
Q

How can the ACL give rotary stability?

A

via its oblique orientation

53
Q

What is the gold standard for ACL reconstruction? When would this not be used?

A

gold standard = patellar tendon graft

- however this takes a long time to take, so for younger athletes, a hamstring tendon graft is a quicker option

54
Q

T/F: Most ACL injuries involve contact with something else.

A

false, 70% are non-contact

55
Q

What are the 3 common factors of ACL injury?

A

females more affected by ACL tear due to:

  1. a greater genu valgus
  2. greater femoral IR
  3. strong quad contraction
56
Q

What is the “valgus collapse”? How can you train people to avoid it?

A

When a person (often female) jumps and then lands hard into valgus, stressing their ACL and MCL (femur IR and ad)

  • train people to land with their knees bend, but land with them straight and not falling inwards
  • teach proper step-down as well, with knee straight over foot and not falling medially
  • strengthen ERs (like glutes) to prevent IR of femur
57
Q

What do many cases of ACL tear result in if proper body mechanics aren’t taught?

A

50% of cases end up with osteoarthritis

58
Q

What is the unhappy triad? How does it occur?

A

injury to ACL, MCL, and medial meniscus (as well as post. capsule)

  • occurs via hyperextension of knee when foot is fixed, coupled with valgus or rotary stress
  • so bad b/c quad is activating, along with passive stretch of ACL = lots of force bringing tibia anterior
59
Q

When is the ACL at maximum passive tension?

A

full knee extension

60
Q

When is the PCL at maximum passive tension? Where is it most lax?

A
  • between 90-120 degrees of flexion = max strain

- lax between 30-40 degrees flexion

61
Q

What’s the normal ROM for knee flexion?

A

130-150 degrees of flexion

62
Q

T/F: PCL is most lax in knee extension.

A

false, lax in 30-40 degrees flexion

63
Q

Could you strengthen quads in a patient that just tore their PCL?

A

yes for SURE, do popliteus too

64
Q

About 50% of PCL injuries involve what other 3 structures?

A
  1. ACL
  2. Meniscus
  3. posterolateral capsule
65
Q

Where is the patella at its most freely-moving point?

A

full KE

66
Q

When does the patella do the moving in KE/KF, in open or closed chain?

A
  • OPEN CHAIN = patella slides on intercondylar groove and follows tibia
  • close chain = intercondylar groove of femur glides on fixed patella
67
Q

Describe when the patella experiences inferior pull, superior pull, etc.

A

full KE = only inferior pull
full flexion = superior pull
midrange = superior and inferior pull

68
Q

What makes up the superior pull? Inferior pull?

A

superior pull = lateral facet and odd facet

69
Q

Why is lateral dislocation of the patella more likely than medial?

A

quad pulls laterally, so does IT band

70
Q

What nerve innervates the knee extensors?

A

femoral n.

71
Q

What nerve is the largest afferent supply to the knee joint?

A

tibial n.

72
Q

Which of these does not innervate the knee flexors?

 a) tibial n.
 b) superficial fibular n.
 c) common fibular n.
 d) femoral n. 
 e) obturator n.
A

b) superficial fibular

73
Q

What does tibial nerve innervate?

A

posterior compartment of leg

  • superficial = gastroc, soleus, plantaris
  • deep = popliteus, deep tibialis posterior, FHL, FDL
74
Q

What does common fibular nerve innervate?

A

branches into superficial and deep, so those are:

  • superficial = lateral compartment (peroneus long/brevis)
  • deep = anterior compartment (tib anterior, EDL, EHL)
75
Q

Foot dorsiflexors are innervated by what?

A

deep fibular n. (muscles = tib anterior, EDL, EHL)

76
Q

What nerve roots give sensory innervation to the knee?

A

L3-5

77
Q

Why can’t you just strengthen the vastus lateralis to decrease lateral patellar tracking?

A

b/c vastus medialis can’t be isolated: need to just strengthen entire quad
- could do just medialis through e-stim though

78
Q

T/F: Passive tension of the patellar ligament offsets quad torque during KE.

A

true

79
Q

What is patella tracking?

A

how the patella moves in the intercondylar groove of the femur: want it to be smooth and stay in there

80
Q

What do the quads do eccentrically? (2)

A
  • control the amount of KF, especially in a squat

- act as shock absorber to attenuate ground reaction forces, countering KF

81
Q

Do we need quads to get out of a chair?

A

yes, duh

82
Q

What are the quads doing in an isometric contraction? (for the knee joint)

A

giving stability and protection

83
Q

When running, what is a big thing the quads need to do?

A

control knee flexion! When you hit the ground, you go into knee flexion to absorb the GRF, and the quads control this

84
Q

Where is the most demand on the quad in open chain? Closed chain?

A

open chain = quad is in highest demand in full KE

closed chain = quad is in highest demand in 90 degrees KF

85
Q

When do the internal torque of extensors match the external torque of the body weight in rising from a squat?

A

at 45-70 of knee flexion

86
Q

Why start a patient in low squats vs deep squats for quad strengthening?

A
  • not as much internal torque needed from knee extensors to offset external torque (of the knee flexors and body weight) when in only 40-70 degrees of knee flexion
  • easier to do these small squats if quads can’t produce enough torque to offset high extensor torque in a deep squat
  • good to train this way for patella as well, gives it good contact
87
Q

What helps increase the internal moment arm for the quads? What 3 factors influence the length of the IMA? (including patella)

A

patella increases quad pull by 5-10x:

  1. shape and postion of patella
  2. shape of distal femur including intercondylar groove depth
  3. migrating axis of rotation
88
Q

What is extensor lag?

A

the last 20 degrees of extension are difficult for patients because they require a lot of quad torque

89
Q

T/F: Upper body weight moment arm increases from 0-90 degrees knee flexion in closed chain.

A

true

90
Q

Organize these in terms of decreasing patellar joint compression force: stair climbing, SLR, walking, deep squat.

A

deep squat -> stairs -> SLR -> walking

91
Q

Compression force magnitude on the patella is a function of what two things?

A

quad contraction and knee flexion angle

92
Q

When is patellofemoral joint compressive force maximized?

A

60-90 degrees flexion

93
Q

T/F: The amount of contact with the patella decreases in a deep squat.

A

true

94
Q

What is the Q-angle and what’s a normal value for it?

A
  • q-angle = angle from line through ASIS to patella, and line from patella to tibial tuberosity; determines quad lateral pull
  • normal = 13-15 degrees (females can be larger than males)
95
Q

A larger Q-angle can lead to what at the knee? (or visa versa)

A

valgus

96
Q

What general factors offset the lateral pull of the patella, keeping the patella in the groove?

A

1) local factors = those acting directly on PFJ

2) global factors = those related to alignment of LE bones and joints distal to PFJ

97
Q

What are the 3 local factors helping to offset lateral pull of patella?

A
  • VMO in good alignment to keep patella medial
  • medial patellar retinacular fibers that blend w/ VMO pull medially
  • raised lateral facet of intercondylar groove prevents lateral pull
98
Q

Explain the global factors affecting the lateral patellar pull.

A

These things increase Q-angle, which increases lateral pull:

  • weak hip abductors: adductors pull femur in, cause valgus
  • hip adductor tightness
  • coxa vara
  • excessive subtalar joint eversion
99
Q

T/F: PT can affect the local factors for patellar issues.

A

false, only global

100
Q

What can a PT do to address the global factors for patellar pull?

A
  • strengthen abductors to decrease genu valgus potential
  • stretch adductors
  • raise arch of foot
101
Q

T/F: Excessive ER of knee can decrease the Q-angle and decrease lateral bowstring force on patella.

A

false, ER can increase bowstring force on patella by increasing Q-angle

102
Q

How do you increase bowstring force? (bad)

A

IR of femur, ER of tibia

103
Q

Why do we not just IR the knee to decrease bowstring force?

A

b/c it will result in foot pronation

104
Q

What muscles resist valgus loading of the knee?

A

pes anserine:

  • ST
  • gracilis
  • sartorious
105
Q

T/F: Popliteus does lateral rotation of femur.

A

true

106
Q

T/F: The hamstrings are dependent on moment arm to generate force.

A

FALSE

107
Q

What actions does the pes anserine muscles do?

A

all flex and IR knee

108
Q

What does the biceps femoris do?

A

flexes and ER knee

109
Q

What has eccentric control over the ER of the tibia during knee extension?

A

the internal knee rotators

110
Q

What needs to happen during early swing phase for the LE to clear the floor?

A

concentric knee flexion

Analysis of Movement (14 decks)

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