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Unit 2 > 10-17b Knee Biomechanics II > Flashcards

10-17b Knee Biomechanics II Flashcards

1
Q

Describe the MCL. What is its clinical significance?

A

It has three layers, blends in with the joint capsule

attaches above medial condyle of the femur and below the medial surface of the shaft of the tibia

force to failure = 799 N

more stable, less mobile, stabilizes medial meniscus = medial meniscus is less mobile and more prone to injury

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2
Q

What is the primary job of the MCL? At what degree of knee flexion is it contributing most to valgus stability?

A

resist valgus forces = valgus stress test
limits external rotation of tibia

resists anterior translation of tibia on femur

at 25% of knee flexion MCL contributes 78% of valgus stress (do stress test here)

at 5% it contributes less

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3
Q

When is the MCL taught? What is its structure when extended and flexed? Clinical significance?

A

taut at full knee extension: helps resist hyperextension

superficial vertical fibers relaxed and oblique fibers are taut during extension

superficial vertical fibers are tight and deep oblique fibers are relaxed during flexion

More injuries when extended due to it being taught

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4
Q

Define Q-angle. Normal degrees?

A

Angle from ASIS (where sartorius attaches), to midline patella, to tibial tubercle

13-15 degrees

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5
Q

Where does the LCL attach? Force to failure? Variations?

A

attaches to proximal/posterior femoral condyle & distal/anterior styloid-fibula

392 N

100% variation

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6
Q

What are the LCL’s primary jobs? Where is it taught?

A

resist external rotation of the tibia on the femur

taut in full extension

helps resist hyperextension

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7
Q

What is the function of the IT band? Where does it insert?

A

Anterolateral support to the knee
Gerdy’s, lateral patella femoral ligament

Knee extension
(IT Band is anterior to knee axis)

Knee flexion
(IT Band is posterior to knee axis)

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8
Q

What is the primary job of the posterior capsule?

A

Resists excessive hyperextension

Genu Recurvatum:
Hyperextension greater than 5°

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9
Q

What is the function of the PLC

A

resists varus stress, external rotation, and posterior translation

dial test

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10
Q

What is the PLC three major stabilizers?

A

LCL
Popliteo-fibular ligament (PFL)
Popliteus muscle and tendon

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11
Q

What is the PLC’s secondary stabilizers?

A

Fabello-fibular ligament (FFL)
Joint capsule
Long head of biceps
ITB

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12
Q

What is the function of the posteromedial corner?

A

Anteromedial rotary stability

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13
Q

What are the three heads of the hamstrings? What are their primary function?

A

semimembranosus (medial meniscus)
semitendinosus (pes sanserine)
biceps femoris (attaches to fibula)

flex the knee and stabilizes the hip

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14
Q

Pes Anserine components? Where is it?

A

Sartorius (anteriorly, Gracilis Middle, Semitendinosus (most lateral)

Anteromedial knee

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15
Q

Knee Extensors: quads

A 
passes over two joints
Rectus femoris
vastus lateralis 
vastus medialis
vastus intermedius
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16
Q

What indicates quad weakness? Where do ind. compensate?

A

Less knee flexion during weight acceptance

less force attenuation
greater TF compressive forces

compensate at hip and ankle

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17
Q

What side of the knee has a buttress for the patella?

A

lateral

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18
Q

apex attaches to what tendon?

A

patellar tendon

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19
Q

Base attaches to what tendon?

A

quadriceps tendon

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20
Q

What are the facets on the posterior patella?

A

odd facet, medial facet, vertical ridge, lateral facet

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21
Q

Is patellofemoral arthritis as prevalent as TF arthritis? What population?

A

yes

especially in post traumatic knee populations?

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22
Q

What plays a part in lateral patellar dislocation

A

IT band on top of retinaculum to keep patella from moving laterally

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23
Q

How does the q angle affect the tendency towards lateral sublux of patella

A

all the tendons are oriented laterally, so the patella tends to move laterally

females have more patellar subluxations

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24
Q

What does normal alignment use?

A

angle b/w femur and tibia

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25
Q

knee abduction

A

ankle pronation

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26
Q

What is a dynamic valgus vs. alignment valgus?

A

vectors are more lateral

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27
Q

What m. prevent lateral patellar dislocation?

A

quadriceps: vastus medialis, vastus medialis obliqus, and VMO combat q angle

28
Q

What’s the pennation angle

A

vastus medialis m. VML = 15-18 degree pennation angle to pull patella superiomedially

VMO = 37 degrees
VMO patella = 50-55 degree pennation angle

fights lateral translation

29
Q

Which side of the trochlea is heightened?

A

lateral

30
Q

What are the static stabilizers against lateral translation?

A

lateral trochlea, medial PF ligament (biggest thickening structure on the medial structure of the knee that provides static stability, medial retinaculum

31
Q

What does a hypoplastic trochlear groove lead to?

A

chronic dislocation

32
Q

What should you train athletes to do to utilize the trochlea best?

A

have them flex their knees

the patella is out of the trochlea for the first 15 to 20 degrees of flexion

33
Q

What structures stabilize against medial translation

A

vastus lateralis, lateral retinaculum (attached to IT band)

34
Q

What are the proximal and distal stabilizers?

A

quad, quadriceps tendon (broad attachment)

patellar tendon to tibial tuberosity

35
Q

infrapatellar fat pad role?

A

fat pad pathology
adipose tissue: highly innervated so can be a source of knee pain
abnormal loads through the fat pad causes thickening
nothing to do with stability

36
Q

What is patella alta/baja? clinical relevance?

A

alta: high knee cap
baja: low knee cap
length of patellar tendon to the tibial tubercle
over length of patella = should be 1
greater than 1.2, knee cap is sitting higher
clinical relevance: if it sits high then its more likely to subluxate (not engaging trochlea until far more knee flexion)
shallow groove and high sitting patella: patella femoral joint problems

37
Q

What are normal patellar kinematics?

A 
proximal/distal translation
anterior posterior translation
flexion/extension
med/lat translation
med/lat tilting
med/lat rotation
38
Q

Where does the patella move when you extend your knee?

A

Located above joint line
Moves proximal
anteriorly,
Patella extends

39
Q

Where does the patella move when you flex your knee?

A

Moves distally,
posteriorly,
flexes

40
Q

Where does the patella normally tilt?

A

laterally due to IT band

41
Q

What are normal patellar kinematics from extension to flexion? Why for each?

A

medial: 0-30 degrees: engages in trochlear groove
lateral: 30-100 degrees
medial > 100 degrees: medial patellofemoral ligament gets taught

42
Q

What is the contact area of the patella from the beginning of flexion? What comes into contact in deep flexion? Clinical significance?

A

contact on distal end
As flexion approaches 90 degrees, the articulating surface moves towards the base to cover the proximal one half of the patella
At 135 degrees of flexion, the odd facet comes into contact
pain can be different depending on the degrees of flexion

43
Q

How does contact area change from 0 to 90 degrees knee flexion?

A

0.8 cm squared to 4.7 cm squared

44
Q

In a straight knee, what two forces are acting on the patella?

A

patellar tendon and quadriceps force

45
Q

As you start to squat what m. is working harder?

A

quad

46
Q

What happens to JRF as you go deeper into a squat?

A

higher

47
Q

How can you reduce someone’s JRF?

A

bring weight backwards towards heels to reduce quad work and bring glutes into play

48
Q

For exercise prescription, what should you avoid?

A

deep squats

49
Q

In open chain, where do you see an increase in quad force?

A

last 20 deg of extension

50
Q

What is JRF for patellofemoral joint?

A

Function of knee flexion and task,
moment arms of Pat lig, Quad Tendon,
Moment arm of patella, quadriceps force

51
Q

What is PFJ stress equal to?

A

JRF/contact area

52
Q

What is PFJ stress at extension at zero deg in regards to JRF and contact area for lex extension?

A

high JRF/low contact area

high stress

53
Q

What is PFJ stress at 30 deg flex in regards to JRF and contact area for leg extension?

A

lower JRF (less quad effort)/higher contact area

54
Q

What is PFJ stress at 90 deg flex in regards to JRF and contact area for leg extension?

A

lowest JRF (no quad activation)/highest contact area

55
Q

What is PFJ stress at 0 deg flex in regards to JRF and contact area for leg press?

A

small JRF/small contact area

56
Q

As you begin to squat, what happens to PFJ stress at 30 deg flexion in regards to JRF and contact area for leg press?

A

higher JRF/higher contact area

57
Q

Why does stress go up in a squat at 90 deg as surface are increases along with the JRF?

A

quads are working harder JRF is big/large contact area
JRF are significantly higher than the forces from change in contact area
stress goes up

58
Q

What is the prevalence of PFPS?

A

all encompassing diagnosis
indicates overuse chronic anterior knee pain
highly prevalent 22.7 percent pop anually
having this younger develops into arthritis later on

59
Q

What are the mechanisms of PFJ pain?

A

local factors, distal factors, proximal factors

the knee is the symptom, but the problem can be somewhere else

60
Q

What proximal factors can cause PFJ pain?

A

hips dropping in frontal plane
brings femur into adduction
which causes valgus

61
Q

What are the local factors that cause a lateral pull on the patella?

A

quad force
IT band
patella position (alta)

62
Q

What are the local factors that oppose a lateral pull on the patella?

A

lateral trochlear grove (hypoplastic)
VMO (atrophy, inhibition, delayed activation?)
medial PF ligament/retinaculum

63
Q

What kind of moment can be assoc. with PFP?

A

higher knee abduction moments

64
Q

What does pronation of the foot do?

A

alters biomechanics at the knee and hip

65
Q

What are the dynamic stabilizers against lateral translation?

A

pennation angle
m. located medially that resist lateral translation

VMO patella at 50 to 55 deg

CMO quad tendon at 37 deg

CML at normal 15 to 18

66
Q

What direction of a vector of force is caused by the patellar and quad tendons on the patella?

A

lateral vector

Unit 2 (29 decks)

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