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S1 Biomechanics > Biomechanics Knee > Flashcards

Biomechanics Knee Flashcards

1
Q

articulations in a common knee capsule

A

medial tibiofemoral
lateral tibiofemoral
patellofemoral

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2
Q

knee alignment: what are the values for

  • genu varum
  • normal
  • excessive genu valgum
A

varum: >180
normal: 170-180
valgum: <170

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3
Q

anterior joint capsule reinforcements of the knee

A

CT
-patellar retinacular fibers (medial and lateral)
quad muscle/tendon
-patellar tendon

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4
Q

lateral joint capsule reinforcements of the knee

A 
CT
-LCL
-lateral patellar retinaculum
-IT band
-lateral coronary ligaments
biceps femoris
popliteus
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5
Q

posterior joint capsule reinforcements of the knee

A 
CT
-oblique popliteal
-arcuate popliteal
gastroc
hamstrings
popliteus
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6
Q

medial joint capsule reinforcements of the knee

A 
CT
-medial patellar retinaculum
-MCL
-medial coronary ligaments
pes anserine muscles
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7
Q

fat pads of knee

  • associated with…
  • function
A

associated with bursae

provide protection and lubrication between femur and patella

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8
Q

fat pads of knee

  • associated with…
  • function
A

associated with bursae

provide protection and lubrication

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9
Q

knee alignment: what are the values for

  • genu varum
  • normal
  • excessive genu valgum
A

varum: >180
normal: 170-180
valgum: <170

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10
Q

menisci

  • composition
  • function
  • anchored to tibia by…
  • other meniscal attachments
A 
fibrocartilage
convert flat tibial plateaus to slightly concave sockets
anchored to tibia by
-ant/post meniscal horns
-coronary ligaments (meniscotibial)
transverse ligament links anterior horns
posterior meniscofemoral ligament
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11
Q

lateral joint capsule reinforcements of the knee

A 
CT
-LCL
-lateral patellar retinaculum
-IT band
-lateral coronary ligaments
biceps femoris
popliteus
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12
Q

posterior joint capsule reinforcements of the knee

A 
CT
-oblique popliteal
-arcuate popliteal
gastroc
hamstrings
popliteus
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13
Q

medial joint capsule reinforcements of the knee

A 
CT
-medial patellar retinaculum
-MCL
-medial coronary ligaments
pes anserine muscles
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14
Q

synovial capsule of knee

  • inside…
  • name of “outpouchings” that minimize friction
  • which ligaments are outside this capsule
A

inside fibrous capsule
outpouchings are called bursae
cruciate ligaments outside synovial capsule

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15
Q

fat pads of knee

  • associated with…
  • function
A

associated with bursae

provide protection and lubrication

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16
Q

plicae

  • what are they
  • why do we care?
A

synovial folds
-remnant of compartmental septa
can become large and fibrous in some people, leading to pain

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17
Q

tibiofemoral joint

  • type of joint
  • how well do they fit together?
A 
bicondyloid joint (medial and lateral)
minimal bony congruency
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18
Q

menisci

  • composition
  • function
  • anchored to tibia by…
A 
fibrocartilage
convert flat tibial plateaus to slightly concave sockets
anchored to tibia by
-ant/post meniscal horns
-coronary ligaments (meniscotibial)
transverse ligament links anterior horns
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19
Q

effect of muscles on meniscus

A

quad and semimebranosus can pull meniscus anterior or posterior

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20
Q

meniscus vascularity and innervation

A 
vascularity
-outer 1/3: red (high)
-middle 1/3: red-white (medium)
-inner 1/3: white (avascular)
innervation
-aneural except at meniscal horns
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21
Q

medial meniscus

  • shape
  • attachments
  • mobility compared to lateral
  • -why?
A 
C-shaped
attachments
-deep MCL
-semimembranosus
-quadriceps
less mobile than lateral meniscus
-MCL attachment
-coronary ligaments
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22
Q

lateral meniscus

  • shape
  • attachments
  • mobility
  • -why?
A 
O-shaped
attachments
-popliteus
-semimembranosus
-quad
-no LCL attachment
greater mobility than MCL
-can move A/P and M/L easier
-no LCL attachment
-less dense coronary ligaments
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23
Q

meniscal functions

A 
contribute to joint stability
-deepen socket
lubrication
guide knee motion
distribute load in weight bearing
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24
Q

of the cruciate ligaments, how do you determine which is the ACL and which is the PCL

A

by tibial attachment

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25
Q

meniscus injury MOI

A

rotation over weightbearing knee

-shear forces

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26
Q

MCL and LCL

-capsular or non-capsular

A

medial: capsular
lateral: non-capsular

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27
Q

MCL functions

A 
primary
-resists external valgus force
secondary
-taut with knee extension
-taut with extremes of medial and lateral tibial rotation
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28
Q

which structures resist valgus force

A

MCL
medial capsule
medial muscles
ACL

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29
Q

LCL functions

A 
primary
-resists varus stress
secondary
-taut with knee extension
-resists extremes of medial and lateral tibial rotation when knee flexed
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30
Q

what structures resist varus force

A

LCL
lateral capsule
IT band
ACL

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31
Q

anterolateral ligament (ALL) function

A

stabilizer for tibial internal rotation

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32
Q

of the cruciate ligaments, how do you determine which is the ACL and which is the PCL

A

by tibial attachment

33
Q

cruciate ligaments

  • location in relation to capsules
  • blood supply from…
A

intraarticular but extrasynovial

blood supply from synovial capsule

34
Q

cruciate ligaments

-functions

A

important in control of knee arthrokinematics

mechanoreceptors present

35
Q

ACL

-portions

A

portions

  • posterolateral
  • -main component; tightest in extension
  • anteromedial
  • -tightest in flexion
36
Q

voluntary axial rotation of the knee (transverse plane)

  • motion greatest at…
  • controlled by…
  • resisted by…
A

greatest motion at 90 flexion
controlled by posterior musculature (horse reins)
resisted by capsuloligamentous tension

37
Q

relationship between ACL and quads

A

quad is ACL antagonist
quad contraction: anterior glide of tibia
effect becomes greater towards full extension
must be careful with ACL surgical rehab towards full extension

38
Q

ACL MOI

A 
usually non-contact
-rotation of trunk over planted foot
-deceleration with knee hyperextension
contact injury
-valgus/varus force
-hyperextension force
39
Q

PCL

  • strength vs. ACL
  • location
  • portions
A

shorter and stronger than ACL
location
-posterior tibia below plateau
-lateral aspect of medial femoral condyle
portions
-anterolateral: larger bundle, more taut in flexion
-posteromedial: more taut in extension

40
Q

PCL functions

A

resists

  • anterior translation of femur on tibia
  • posterior translation of tibia on femur
  • end range flexion
  • extremes of varus, valgus, and rotation
41
Q

what is the PCL antagonist

A

hamstrings

42
Q

PCL MOI

A

fall on a flexed knee

43
Q

knee axis of rotation during flexion/extension

  • what is the axis
  • location of axis
  • influenced by…
A

medial-lateral
not fixed: migrates with ROM
influenced by contour of condyles

44
Q

voluntary axial rotation of the knee (transverse plane)

  • motion greatest at…
  • controlled by…
  • resisted by…
A

greatest motion at 90 flexion
controlled by posterior musculature (horse reins)
resisted by capsuloligamentous tension

45
Q

automatic rotation of knee (transverse plane)

  • aka _____
  • when does it occur?
  • caused by…
  • purpose
A 
aka "screw-home" mechanism
mechanically involuntary coupled rotation that occurs in final 15 extension
caused by
-asymmetry of femoral articular surfaces
-tension in ACL and PCL
-lateral "pull" of quads
"locks" the knee in full extension
46
Q

how does screw-home mechanism occur during open chain actiion

A

motion of the lateral TF compartment stops before motion of the medial TF compartment
tibia laterally rotates on the femur as knee fully extends
ligaments and capsule tight, “screwing home” or “locking” the knee

47
Q

relationship between tibiofemoral rotation and PF contact area
-implication

A

increased tibiofemoral rotation corresponded to decreased PF contact area in subjects with PFP
less contact = more PF stress

48
Q

tibiofemoral arthrokinematics

  • OKC extension
  • CKC extension
A 
OKC
-concave on convex
-anterior roll and glide
-tibial lateral rotation 
CKC
-convex on concave
-anterior roll, posterior glide
-femoral medial rotation
49
Q

tibiofemoral arthrokinematics

  • OKC flexion
  • CKC flexion
A 
OKC
-tibia medially rotates on femur
-posterior roll and glide
CKC
-femur laterally rotates
-posterior roll, anterior glide
50
Q

knee

  • close packed position
  • loose packed position
A

close
-full extension, lateral rotation of tibia on femur
loose
-25-30 degrees flexion

51
Q

genu varum and valgum

-lead to leading of what compartments

A

varum
-medial compartment loading
valgum
-lateral compartment loading

52
Q

genu recurvatum

  • defined as…
  • resisted by…
  • may be result of…
  • consequence
A 
excessive (>10) knee hyperextension
resisted by passive tension in posterior capsule
may be result of
-neuromuscular disease
-postural habit
worsens with age
consequences
-decreased blood supply down back of leg
-places excessive stretch on posterior structures
53
Q

muscle innervation (peripheral nerve)

  • knee extensors
  • knee flexors/rotators
A 
extensors
-femoral nerve
ST, SM, BF long
-tibial portion sciatic
BF short
-peroneal portion sciatic
sartorius
-femoral
gracilis
-obturator
54
Q

PF joint

  • when is contact area greatest
  • when is stability greatest
A

contact area greatest in flexion
most stable in flexion
least stable in extension

55
Q

PF movements

-name of movement and plane movement occurs in

A

tilt: transverse
spin: frontal
shift: medial-lateral translation
flexion/extension (sagittal)

56
Q

patellar tracking in
-extension
-flexion 0-30
flexion >30

A

extension: slightly laterally shifted
flexion 0-30: shifts and tilts medially
flexion >30: shifts and tilts laterally

57
Q

PF minimal movement

A

5 mm total shift

5 degrees total tilt

58
Q

what is the Ratio of Insall and Salvati

-ranges

A

patellar tendon length / patellar height
normal: 0.8-1.2
patella alta: >1.2
patella infera (baja): <0.8

59
Q

muscle innervation (root level)

  • knee extensors
  • knee flexors/rotators
A

extensors: L3, L4
flexors: S1, S2

60
Q

muscle innervation (peripheral nerve)

  • knee extensors
  • knee flexors/rotators
A 
extensors
-femoral nerve
ST, SM, BF long
-tibial portion sciatic
BF short
-peroneal portion sciatic
sartorius
-femoral
gracilis
-obturator
61
Q

%torque of extensors created by

  • rectus femoris
  • vasti group
A

rectus femoris: 20%

vasti: 80%

62
Q

knee extensor synergist

  • location
  • function
A

articularis genu
inserts on suprapatellar bursa
pulls suprapatelar pouch out of the joint

63
Q

knee extensor eccentric contraction examples

A

sitting down

stair descent

64
Q

in the frontal plane, what is the direction of the overall pull of the quads

A

lateral

65
Q

medial tibial rotators

A 
SM
ST
gracilis
sartorius
popliteus
66
Q

in a CKC, at what point in the ROM is the torque demand the greatest

A

in flexed position

-greatest moment arm

67
Q

patellofemoral joint reaction force (sagittal plane) equals…
-compressive or tensile force

A

force of quadriceps + force of patellar tendon

compressive force

68
Q

patellofemoral joint reaction force (frontal plane)

  • direction
  • due to…
A

lateral

due to net lateral quadriceps force

69
Q

lateral pull of quadriceps on patella is resisted by…

-local factors

A

local

  • vastus medialis
  • intercondylar groove (lateral)
  • medial patellar retinaculum (medial PF ligament)
70
Q

lateral pull of quadriceps on patella is resisted by…

-global factors

A

tibiofemoral alignment

  • frontal plane
  • transverse plane
71
Q

knee flexor synergists

A

sartorius, gracilis, and popliteus
-flex and IR tibia
popliteus

72
Q

lateral tibial rotators

A

BF

TFL

73
Q

how do knee flexors control OKC osteokinematics during gait

A

eccentric action in walking gait

concentric action in running gait

74
Q

why are the knee flexors necessary for control of CKC osteokinematics

A

needed for simultaneous control of multiple degrees of freedom across hip and knee
control high velocity movements

75
Q

poor control of knee flexors in CKC can lead to…

A

ACL tearing

76
Q

knee flexion torque

  • greatest torque at…
  • greatest moment arm between…
A

torque greatest at 20 extension

moment arm greatest between 50-90 flexion

77
Q

length vs. leverage in relation to force production in knee flexors

A

length-tension relationships more important in torque production than leverage
hamstrings produce greater torque in relatively elongated position

78
Q

knee rotation torque

-at what angle do rotators have greatest MA?

A

90 degrees

79
Q

popliteus has greatest moment arm for rotation torque at…

A

40 degrees flexion

S1 Biomechanics (12 decks)

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