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Semester 2 FS Exam 8 > Knee Joint > Flashcards

Knee Joint Flashcards

1
Q

Knee Joint

A

largest and most complex joint
most stability comes from soft tissue, not bone
provides mobility for foot in space

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2
Q

What are the two distinct articulations of the knee joint?

A

patellofemoral and tibiofemoral

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3
Q

Net forces in knee joint during dynamic activities?

A

2 -3 x BW in normal gait
5 - 6 x BW in running and stair climbing
10 x BW in single leg standing in basketball

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4
Q

Mechanical Axis

A

connection between hip and knee joint centers
line of action runs between hip and knee
shape defines which stresses the structure experiences
Bowing out = compression medially and tension laterally
norm = 3 degrees from vertical

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5
Q

The bigger the difference between the mechanical and anatomical axes ______ ???

A

the more compressive and tensile forces. if there is no difference between the two, the force will only be compressive.

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6
Q

Anatomical axis

A

runs along the shaft of the femur
normal = 6 degrees
lateral to the mechanical axis!!

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7
Q

Which ligament is very broad and is connected to the joint capsule?

A

MCL

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8
Q

Femur condyles (ovoid)

A

medial condyle larger and projects farther down, making the femur oriented laterally (femoral shaft obliquity) (anatomical axis)

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9
Q

which condyle experiences more load?

A

medial femoral condyle

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10
Q

which condyle is more in line with the shaft of the femur?

A

lateral

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11
Q

patellar surface

A

saddle shaped groove

lateral patellar surface is longer

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12
Q

when are the MCL and LCL taut?

A

taut in extension, slack in flexion

tight ligaments = more joint stability

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13
Q

Tibial plateaus

A

Medial condyle/tibal plateau is 50% larger than the right and the cartilage is 3x thicker than the right.
Due to the mechanical axis, the medial condyle takes on more force than the lateral.

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14
Q

Patellomeniscal ligaments

A

enlargements of the joint capsule

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15
Q

transverse ligament

A

located anteriorly, connects the menisci

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16
Q

Medial meniscus attaches to ___ and ____

A

MCL and semimembranosus

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17
Q

lateral meniscus attaches to ___ and ____

A

PCL and popliteus

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18
Q

coronary ligaments

A

connect meniscus to tibia underneath

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19
Q

lateral vs medial meniscus shape

A 
lateral = almost a complete circle
medial = C shaped
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20
Q

menisci withstand ____

A

tension! resist stretch! do not withstand compression

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21
Q

Function of menisci

A
  1. stabilize the joint - deepen articular surfaces
  2. shock absorption - improved congruency of joint surfaces
  3. force distribution within the joint
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22
Q

removing the menisci

A

increases contact area by 50%
coefficient of friction increases by 20% intrajoint
menisci = asymmetrical wedge-shaped

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23
Q

menisci vascularization

A

avascular structures, so they get their vascularization from the synovial membrane and joint capsule
meniscus has a free end (unattached) inside the joint, which helps synovial fluid move between the joint and decreases friction

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24
Q

Role of menisci during flexion

A

move/deform posteriorly with flexion

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25
Q

role of menisci during extension

A

move/deform anteriorly with extension

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26
Q

Role of menisci in a normal knee during extension

A

Path of instantaneous center of rotation (ICOR):

  • moves posteriorly and then anteriorly
  • moves superiorly
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27
Q

which way does the path of ICOR move with flexion?

A

inferiorly

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28
Q

Knee without meniscus (ICOR)

A

ICOR is variable
more glide in AP direction
early degeneration of cartilage

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29
Q

A loss of the patella results in:

A

18-20% loss of motion

48-50% loss of effectiveness of quads in extension

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30
Q

What does it mean that the patella is the least congruent joint in the body?

A

it has a large articular surface but the contact area is very limited during motion in different positions

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31
Q

Patella

A

anatomic pulley - friction reduction
largest sesamoid bone in the body
least congruent joint in the body
improves mechanical advantage of quads

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32
Q

The odd facet makes up what percentage of the posterior aspect of the patella?

A

30%

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33
Q

Articular facets

A

slightly convex
angle between medial and lateral facets is 138 degrees
lateral facet larger than medial facet

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34
Q

At what angle of knee flexion is there the most congruency with respect to the articular surface of the patella and the femoral groove?

A

90 degrees knee flexion

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35
Q

Patella Tendon Moment Arm (PTMA)

A

largest MA of patellar tendon is at 45 degree angle

the best ability of the quads to produce torque is when the knee is at a 45 degree angle

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36
Q

Patella Alta

A

patella rides too high on femoral condyles

patellar groove is shallow and patella has a tendency to dislocate in lateral direction

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37
Q

Patella Baja

A

patella rides too low on femoral condyles
due to patellar tendon shortening after surgery or injury
MA and effectiveness of quads decreases

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38
Q

Which aspects of the facets are in contact with the femoral condyles in patella baja?

A

lateral part of lateral facet and odd facet. the result of this is that the forces are concentrated in a smaller area

39
Q

Genu valgum

A

abnormal angulation of tibia away from midline
leg mechanical axis is displaced laterally
medial structures = tensile stress
lateral structures = compressive stress

40
Q

Knock kneed

A

genu valgum

41
Q

Describe the load on the lateral compartment of the knee in genu valgum

A

more load on lateral compartment of knee between lateral condyle of femur and lateral tibial plateau
articular cartilage is already thinner laterally, and thins due to compressive stress, increasing risk for OA

42
Q

Genu varum

A

medial structure = compressive stress
lateral structures = tensile stress
abnormal angulation of tibia towards the midline
leg mechanical axis is displaced medially
MCL = slack
LCL = tension

43
Q

bow legged

A

genu varum

44
Q

Genu recurvatum

A

tibia is tilted in the anterior direction
tibial plateaus are not horizontal, so the load from the femur is on the anterior aspect of the tibia
flexors of the knee are constantly active to control the passive load

45
Q

Genu recurvatum

A

abnormal angulation of tibia anteriorly
leg mechanical axis is displaced anterioly
anterior structures = compression
posterior structures = tension

46
Q

excessive strain/torque on which structures in genu recurvatum?

A

excessive knee hyperextension
excessive strain on ACL
excessive extension torque during standing

47
Q

typical Q angle

A

15 degrees

abnormal = >20

48
Q

what is the Q angle influenced by?

A

location of patella
knee joint alignment on frontal plane
femoral and tibial torsions

49
Q

Q angle in valgus

A

> 15 (greater Q angle = increased likelihood for patellar dislocation in lateral direction)

50
Q

Q angle in varus

A
51
Q

Patellar ligament

A

a continuation of the quad tendon

52
Q

Bowstring effect

A

draw patella laterally

causes chondromalacia from chronic stress

53
Q

Chondromalacia

A

type of OA
inflammation and softening of cartilage
involves bony structures

54
Q

knee movements on sagittal plane

A

flexion and extension

55
Q

knee movements on frontal plane

A

valgus and varus (about 5 degrees in each direction)

56
Q

knee movements on transverse plane

A

IR/ER with knee at 90 degrees flexion

57
Q

function of articularis genu muscle

A

moves bursa out of the way during knee extension

58
Q

the synovial membrane gives rise to _______ and wraps around the ____ and ____

A

gives rise to multiple bursal structures and wraps around the ACL and PCL
cruciate ligaments are outside the synovial membrane but inside the joint capsule

59
Q

MCL

A

longer, wider, and closer to the capsule than the LCL

tight in extension, slack in flexion

60
Q

two parts of MCL

A

anterior and posterior

anterior portion is tight in flexion

61
Q

location of MCL

A

runs from medial femoral epicondyle to the tibia

62
Q

location of LCL

A

from lateral femoral epicondyle to fibular head

63
Q

function of LCL

A

resists varus stress/force and ER of tibia

tight in extension

64
Q

function of MCL

A

resists valgus stress/force
resists ER and IR of tibia
resists anterior translation of tibia along with ACL

65
Q

the MCL connects to which two structures?

A

medial meniscus and capsule

66
Q

3 bands of the ACL

A

anteromedial
intermediate
posterolateral

67
Q

origin/insertion of ACL

A

anterior intercondylar eminence of tibia to posterior part of the medial aspect of the lateral femoral condyle

68
Q

functions of ACL

A

resists anterior tibial translation, hyperextension, and tibial IR
resists anterior movement of the tibia on the femur (or posterior movement of the femur on the tibia)

69
Q

when is the ACL tight?

A

in extension

70
Q

when is the PCL tight?

A

in flexion

71
Q

location of PCL

A

posterior intercondylar eminence to lateral aspect of medial femoral condyle

72
Q

name the two bands of the PCL

A

anterolateral

posteromedial

73
Q

functions of PCL

A

resists posterior tibial translation (posterior motion of tibia on femur)
also resists flexion

74
Q

common symptom after ACL injury

A

quad weakness

knee flexion is a protective mechanism for fear of reaching extension position by using quads

75
Q

PCL and PTT

A

PCL resists PTT up to 90 degrees of knee flexion, and diminishes after that

76
Q

PCL effect on PTT

A

PCL limits PTT until 90 degrees of flexion, and then decreases at higher flexion angles (does not help limit flexion in deep squat position)

77
Q

Which ligaments limit hyperextension?

A

Arcuate popliteal, oblique popliteal, ACL

78
Q

function of arcuate popliteal ligament

A

reinforces posterolateral capsule
resists varus stress/impact
helps LCL
limits hyperextension

79
Q

function of oblique popliteal ligament

A

reinforces posteromedial capsule
resists valgus stress
limits ER
limits hyperextension

80
Q

function of medial and lateral retinaculum

A

controls movement of the patella in the medial and lateral direction

81
Q

ITB attachments

A 
Iliopatellar band (causes lateral pull on patella)
lateral tibial tubercle (Gerdy's tubercle) (assists ACL in resisting anterior translation of tibia on femur) (resists varus stress)
82
Q

Which structures pull the patella laterally?

A

lateral retinaculum, ITB, iliopatellar band

83
Q

Knee function stability

A 
no bony stops to motion
joint geometry change of menisci (1)
passive restraint from ligaments (2)
active muscles (3)
compressive load ( more compressive load = more joint stability?)
84
Q

motion of femur on tibia during closed kinetic chain

A

proximal on distal
convex on concave
roll and glide in opposite directions

85
Q

motion of tibia on femur during open kinetic chain

A

distal on proximal
concave on convex
roll and glide in same direction

86
Q

roll and glide during closed kinetic fhain

A

flexion: roll posteriorly and glide anteriorly
extension: roll anterior and glide posterior
menisci responsible for translation/glide that occurs during rolling

87
Q

screw-home mechanism

A

15 degrees of tibial rotation occurs during final 30 degrees of knee extension. most of this rotation occurs during final 5 degrees of knee extension because of bony asymmetry (medial condyle projects farther than lateral condyle, creating IR) and because of ligament tension

88
Q

open chain screw home mechanism

A

during terminal extension, ER of the tibia on the femur occurs

89
Q

closed chain screw home mechanism

A

during terminal extension, IR of the femur on the tibia occurs

90
Q

peak ability of muscles to do IR/ER of knee is when?

A

at 30-45 degrees of knee flexion. decreases beyond 45 degrees due to decreased muscle length

91
Q

ER of knee

A

biceps femoris

92
Q

IR of knee

A

semi ten and mem, sartorius, gracilis, popliteus

93
Q

when do the quads produce maximum torque?

A

45 degrees of knee flexion (due to muscle length and muscle MA)

Semester 2 FS Exam 8 (1 decks)

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