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MSK 2 test 1 > Biomechanics of the knee > Flashcards

Biomechanics of the knee Flashcards

1
Q

Tibiofemoral joint type

A

double condyloid - prevent motion in the frontal plane

2° of freedom
Flexion extension in sagittal plane
medial lateral rotation in transverse plane

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2
Q

Tibiofemoral femoral articular surface

A

Large AP convexity
Small curvature Posterior

medial condyle is longer than lateral and extends further distally for the angled femur

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3
Q

tibiofemoral tibial articular surface

A

Medial and lateral tibial plateau- concave and slopes posterio inferiorly

medial tibial plateau is 50% larger, oval and long , and the articular cartilage is three times thicker than the lateral

Lateral plateau is more circular

meninsci Compensate for incongruency

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4
Q

Function of the meniscus

A

increases stability by deepening the tibial plateau

decreases the friction by 20%

Increases contact area by 70%

Enhances proprioception via mechano receptors

attenuates forces

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5
Q

medial meniscus

A

c shaped
Firm attachment to the deep layers of the MCL
Thick posteriorly

thicker on periphery thinner along inner margin

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6
Q

Lateral meniscus

A

o shaped
Loose attachment to the lateral capsule
Uniform thickness

thicker on periphery thin along inner margin

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7
Q

menisci transmit how much percent of imposed load at the knee

A

50 to 60%

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8
Q

after a complete menisectomy, the average load per unit area

A

two times on the femur
6 to 7 times on tibial condyle

Shock absorption capability is reduced by 20%

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9
Q

menisci vascularization

A

initially, well vascularized

Recedes to periphery by age 11

in adults, vascularized by capillaries from the joint capsule and synovial membranes

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10
Q

tibiofemoral ligaments control and resist

A

hyper extension
Varus valgus
AP displacement of tibia on femur
Medial lateral rotation of tibia on femur
Combination of AP and rotation

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11
Q

collateral ligaments

A

MCL
LCL

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12
Q

MCL

A

prevent abduction, valgus stress

attaches 7 to 10 cm below joint line

Assist in prevention of anterior tibial translation

Attaches to joint capsule and medial meniscus

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13
Q

MCL dynamic

A

all fibers taut in full extension

anterior fibers also taut in mid range flexion while posterior fibers are more on slack

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14
Q

LCL

A

prevents adduction, varus stress

No attachment to capsule or meniscus

Assist with internal rotation and external rotation restraint

Greater laxity than MCL
Pencil like band of tissue

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15
Q

LCL Dynamic

A

tight in knee extension
Loosen as knee flexes

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16
Q

Anterior cruciate ligament

A

Anterior aspect of tibial, posterior aspect of LFC

three bundles - anteromedial
posterolateral
Intermediate

33 mm in length
11 mm in diameter

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17
Q

ACL functions

A

prevent anterior tibial translation

checks hyperextension

works with the MCL to stabilize against valgus
With assistance from hamstrings

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18
Q

Posterior cruciate ligament

A

One of the strongest ligaments of the body

Shorter and less oblique than the ACL

Rarely injured

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19
Q

PCL functions

A

prevents posterior translation of the tibia on femur

primary restraint to posterior displacement

Minor restraint to varus and valgus

20
Q

genu valgum

A

TF angle <165
Increased lateral compressive forces

21
Q

genu varum

A

TF angle >180
increase medial compressive forces

22
Q

Q angle

A

angle formed by the line drawn from ASIS to mid patella and line from mid patella to tibial tuberosity

Males 10 to 14°
Females 15 to 17°

23
Q

knee flexion extension ROM

A

flexion- 130 to 140°
Extension - 5 to 10° of hyper extension

24
Q

genu recurvatum

A

Excessive hyper extension of the knee

25
Q

closed chain AROM related to ankle

A

decreased dorsiflexion- decreased knee flexion

Decrease plantarflexion- decreased knee extension

26
Q

Gait ROM needed at knee

A

60 to 70°

27
Q

On or off toilets, ROM

A

75°

28
Q

stair climbing ROM

A

70-80°

29
Q

in and out of bath ROM

A

90°

30
Q

sit and rise in chair ROM

A

90°

31
Q

Advanced function, ROM

A

115°

32
Q

Full extension and rotation

A

Rotation restricted by interlocking of femoral and tibial condyles

33
Q

90° of flexion and rotation

A

ER- 0 to 45°
IR - 0 to 30°

34
Q

screw home mechanism

A

during the last 5° of extension

Lateral femoral condyle shorter

Medial tibial condyle continues to move on the femur

Lateral rotation of tibia on femur or internal rotation of femur

35
Q

screw home mechanism augmented by

A

Tension on ACL
Lateral pull of quadriceps

36
Q

flexion and screw home mechanism

A

Flexion requires unlocking
Femur laterally rotate on tibia
Tibia must mediately rotate

37
Q

popliteus and screw home mechanism

A

OKC- moves tibia medial IR
CKC - moves femur lateral ER

38
Q

patellofemoral joint

A

Posterior surface covered with thick hyaline cartilage

patella slides within trochlear groove

39
Q

patellofemoral facets

A

medial- flat to slightly convex
Lateral - longer than med
Odd - medial angle

40
Q

PF joint contacts

A

first consistent contact is between 10 to 20° of flexion

By 90° all aspects of facets have made contact except odd facet

At 135° contact is on odd and lateral facets

41
Q

PF compression

A

As the angle of knee flexion increases so do compressive forces

Greatest PF compression force at 90° flexion

As Q angle increases so will lateral vector due to pull of the quads

42
Q

PF joint reaction force

A

Fully contracted, quad and full extension produces little PF contact force

medial facet bears most force

PF forces
Foot strike knee flex 10 to 15°- 50% of body weight

60° knee flexion- 3.3 times bodyweight

130° knee flexion - 7.8 times bodyweight

43
Q

transverse stabilizes for PF

A

medial and lateral reticulum

VMO and VL

MPFL

44
Q

longitudinal stabilizers for PF

A

Quad tendon
patellar tendon

45
Q

what else stabilizes pf

A

IT band
Lateral wall of femoral groove

MSK 2 test 1 (11 decks)

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