lecture 5: biomecanics of the knee Flashcards
1
Q
what are the two articulations in the knee
A
tibiofemoral
patellofemoral
(tibia, patella, femur)
2
Q
the superior tibiofibular involves what bones
A
tibia
fibular
3
Q
femur is angled laterally or medially from the vertical
A
inferior side goes in medially
4
Q
in the femur, the medial and lateral condyles articulate with what
A
the tibia
5
Q
the patellar surface of the femur articulates with what
A
patella
6
Q
are there any differences in the femoral condyles
A
yes, diff sizes
7
Q
true or false: the lateral condyle articulating surface is larger anterior-posterior
A
false, the medial condyle
8
Q
why is the medial condyle surface larger anterior to posterior
A
largest area = helps distribute the forces
9
Q
lateral condyle anterior surface extends further anteriorly, why>?
A
prevent lateral patella dislocation
10
Q
true or false, since the medial condyle extends further anteriorly, it prevents patella discloation
A
false, lateral
11
Q
which femoral condyle is more curved
A
medial femora condyle
12
Q
what helps prevental lateral patellar dislocation
A
the fact that the lateral condyle anterior surface extends further anteriorly
13
Q
in the tibia, which tibial plateau is larger
A
the medial tibial plateau is larger than the lateral plateau
14
Q
why is the medial tibial plateau larger than the lateral plauteau
A
increased medial loading
helps decrease stress (force/area)
15
Q
why is there more medial loading on the knee
A
because the ground reaction force is more towards the middle
16
Q
what are the meniscie
A
fibrocartilage disks
17
Q
what shape are the menisci
A
wedged shape
18
Q
where are the menisci located
A
between the femur and tibia
19
Q
is there blood supply to the menisci
A
some blood supply peripherally
(but there is an avascular cetner)
20
Q
if you tear the menisci peripherally, can it be repaired
A
possibile beacuse there is some blood supply there
21
Q
what is the function of the menisci
A
increase contact area between tibia and femur (approximately double the area)
(stress= force/area)
22
Q
when there is a meniscu tear, why would it be a bad idea to remove it the menisci completely
A
more joint loading and degeneration
23
Q
what type of joint is the knee
A
modified hinge joint
24
Q
how many degrees of freedom in the knee (modified hinge joint)
A
2 degrees of freedom
25
what are the movements possible at the knee joint
flexion and extension
medial and lateral rotation
(minimal adduction and abduction)
26
what is the disagreement about degrees of motion in the knee
that there at 6 DOG
(conjuct rotation and translation) but we have no control over these accessry motions
27
medial and lateal rotation (transverse plane) of the knee happens along what axis
sup/inf
28
flexion and rotation (sagital plane) of the knee happens along what axis
medial and lateral axis
29
adduction and abduction (frontal plane) happens aling what axis
arond the ant/post axis
30
what is the normal range of motion for knee flexion
140
31
what is the normal range of motion for knee extension
0
32
what is the normal range of motion for knee external/lateral rotaiton
45
33
what is the normal range of motion for knee internal/medial
30
34
what is the normal range of motion for knee abduction/adduction
a few degrees
35
what is the knee flexion needed for walking
67
36
what is the knee flexion needed for sit to stand
99 (104 in previous example)
37
what is the knee flexion needed for sit to stand (low chair)
105
38
what is the knee flexion needed for stairs
99
39
what is the knee flexion needed for getting out of bath
138
40
understand the gait saggital knee angle graph
.
41
during heel strike, is the knee angle in extension or flexion
in extension
42
what happens at 20% of gait cycle in terms of the knee angle
there is an increase in knee flexiion beacuse we are at fullweight bearing position
in flexion to decrease the impact of the ground reaction force and absorb shock
43
from 20-40% what happens to the sagital angle of the knee
goes back into extension to help clear foot off the ground
44
what happens to knee angle between 60-100% of gait cycle
initially, knee flexion increases because foot is in swing phase and need to clear the gound
from 80-100%, knee goes back into extension to prepare the leg for ground contact
45
what is the peak knee joint reaction force for level walking
3-4 BQ
46
what is the peak knee joint reaction force for stair climbing
5.4
47
what is the peak knee joint reaction force for lifting
2.12
48
what is the peak knee joint reaction force for jogging
12.4 BW
49
what is the peak knee joint reaction force for squatting
7.6 Bw
50
what requires peak knee joint reaction force of 3-4 BW
level walking
51
what requires peak knee joint reaction force of 5.4 BW
stair climbing
52
what requires peak knee joint reaction force of 2.12 BW
lifting
53
what requires peak knee joint reaction force of 12.4 BW
jogging
54
what requires peak knee joint reaction force of 7.6 BW
squatting
55
during rotation, direciton of intraarticular glide is predictid by what
shape of joint surface
56
if bone with the concave surface moves on the convex surface, the concave articular surface glides where
in the same direction as the bone segments roll
57
if bone with the convex surface moves on the concave surface, the convex articular surface glides where
in the direction oppostie of the bone rolling motion
58
true or false: the knee DOES NOT follow the convex-concave rule!
true
59
during knee flexion (closed kinetic chain), explain the joint surface motion
lateral femoral condyle moves posterior with knee flexion
medial femoral condyle movement is less clear
60
during knee flexion (closed kinetic chain), what is the motion of the femoral condyles
lateral femoral condyle moves posterior with knee flexion
medial femoral condyle movement is less clear
61
during knee flexion (closed kinetic chain), does the lateral femoral condyle move posterior or anterior
posterior
62
explain the screw home mechanism (overall)
lateral (external) rotation of tibia on femur during extension (open kinetic chain)
medial (internal rotation) of femur on tibia during extension (closed kinetic chain)
63
during knee flexion (closed kinetic chain), what is the motion of the femur
femur laterally rotates wrt tibia
posterior roll of femur - contact migrates posterior
lateral femur condyle translates posterior wrt tibia
medial femur condyle moves less than lateral sade
64
during knee extension (closed kinetic chain), what is the motion of the femur
femur medially rotates wrt to tibia
anterior roll of femur - cotnact migrates anterior
lateral femur condule translates anterior wrt tibia
medial femur condyle moves less than lateral side
65
during knee flexion (closed kinetic chain), the femur rotates laterally or medially wrt tobia
laterally
66
during knee flexion (closed kinetic chain), is there posterior or anterior roll of the femur
posterior roll of the femur, contact migrates posterior
67
during knee flexion (closed kinetic chain), how does the lateral femoral condyle move
translates posterior wrt tibia
68
during knee flexion (closed kinetic chain), how does the medial femoral condule move
moves less than the lateral side
69
during knee extension (closed kinetic chain), the femur rotates laterally or medially wrt tobia
medially
70
during knee extension (closed kinetic chain), is there posterior or anterior roll of the femur
anterior roll of femur (contact migrates anterior)
71
during knee extension (closed kinetic chain), how does the lateral femoral condyle move
translates anterior wrt tibia
72
during knee extension (closed kinetic chain), how does the medial femoral condyle move
moves less than the lateral side
73
during Knee flexion (open kinetic chain), explain movement of tibia
* Tibia medially rotates w.r.t. to the femur
* Posterior roll of tibia- contact migrates posterior
* Lateral tibia plateau translates anterior w.r.t. femur
* Medial tibia plateau moves less than lateral side
74
during Knee extension (open kinetic chain), explain movement of tibia
* Tibia laterally rotates w.r.t. to the femur
* Anterior roll of tibia- contact migrates anterior
* Lateral tibia plateau translates posterior w.r.t. femur
* Medial tibia plateau moves less than lateral side
75
during knee flexion (open kinetic chain) does the tibia rotate laterally or medially wrt to the femur
tibia medially rotates wrt to the femur
76
during knee extension (open kinetic chain) does the tibia rotate laterally or medially wrt to the femur
the tibia laterally rotates wrt to femur
77
during knee flexion, is there anterior or posterior roll of the tibia
posterior roll of the tibia (contact migrates posterior)
78
during knee extension, is there anterior or posterior roll of the tibia
atnerior roll of the tibia (contact migrates anterior)
79
during knee flexion, what is the movement of the lateral tibia plautea
translates anterior wrt femur
80
during knee extension what is the movement of the lateral tibia plautea
translates posterior wrt to femur
81
during knee flexion, what is the movement of the medial tibia plautea
moves less than lateral side
82
during knee extension, what is the movement of the medial tibia plautea
moves less than the lateral side
83
what is axis 1 of the mechanical axis angle
center of femoral head to center of knee
84
what is axis 2 of the mechanical axis angle
center of ankle to center of knee
85
what is the angle normal angle between axis 1 and 2 for the mechanical axis angle
normal is 2 degrees varus
86
explain varus of the knee
distal segment (tibia) deviates laterally on proximal segment (femur)
smaller than 180
87
in varus of the knee, is the angle greater or less than 180
less than
88
explain varus of the knee
distal segment (tibia) deviates laterally on the proximal segment (femur)
greater than 180
89
in valgus of the knee, is the angle greater or less than 180
greater than
90
what is knee osteoarthritis
deterioration of joint tissue (bone cartilage)
91
which allignment increases the risk of medial compartment knee OA dev and progression
varus allignment
92
which allignment increases the risk of lateral compartment knee OA dev and progression
valgus allignment
93
varus allignment increases the risk of BLANK compartment knee OA dev and progression
medial
94
valgus allignment increases the risk of BLANK compartment knee OA dev and progression
lateral
95
why is medial compartment knee OA dev and progression more common
because GRF is inclined more medially
96
explain how varus causes more medial loading
varus creates a greater moment arm which increases the adduction moment
this wants to pull the medial tibia inwards
this increases medial loading
97
higher adduction loading increases medial or lateral loading
medial
98
how do you correct knee allignment
High tibial osteotomy
99
to correct limb allignment, what do you have to chagne
change the mechanical axis angle (usually less varus)
100
when you are correcting limb alignment and changing the mechanical axis angle, you are usually attempting to get less varus or valgus
less varus
101
allighment correction of the knee decreases what
medial compartment loading
102
alignment correction of the knee slows what
knee OA disease progressions
103
Explain the results of the study of high tibial osteotomy
decrease in mechanimal axis angle and knee adduction moment during gait 2 years after high tibial osteotomy
104
medial collateral ligament stabilizes against what force
valgus (abductor force)
105
what is more commonly injured, medial or laterall collateral leg
medial
106
how is the medial colalteral lig usualy injured
knee planted
knee struck on the outside
107
the lateral collateral ligament stabilizes against what force
varus (adductor force)
108
true or false; tthe lateral collateral ligament stabilizes against valgus force
false, varus
109
explain how the lateral collateral lig is injured
less common, usually with multilig injuries
110
what is the function of the anterior cruciate lgi
resist anterior glide of tibia (may also resist rotation, varus/valgus)
111
what is the funtcion of the posterior cruciate lig
resist posterior glide of tibia, rotation, varus and valgus
112
what is the mecahism for a contact injury of thje acl
foot planted, femur driven posterior
rotation
113
what is the mechanism for a non contact acl injury
landing, deceleration, pivoting/cuttibg
knee/hip in extension and valgus
quadriceps overload
114
are contact or non contacl acl injuries more common
non contact (more common in fems)
115
how can quadriceps overload cause an acl injury
pulls tibia anterior (higher anterior shear, pulls tibia forward and strains acl)
116
explain the vulnerable position for the back for acl mechanism of injury
forward flexed
rotated oppostie side
117
explain the vulnerable position for the hips for acl mechanism of injury
adduction, internal rotation
118
explain the vulnerable position for the knee for acl mechanism of injury
less flexed, valgus
119
explain the vulnerable position for the tibial rotation for acl mechanism of injury
internal or extenal
120
explain the vulnerable position for the landing patter for acl mechanism of injury
one foot out of control or unbalanced
121
there are prevention programs designed to improve dynamic alighment , but did they work ?
metaanalysis: fifa 11 reduced injuries by 39% in soccer players
decreased knee valgus moments in female children during double leg jump but not other activiesi (no change in knee angles)
122
what happens to moment arm of the trunk with knee flexion
moment arm of the trunk weight increases with increases knee flexion (takes more quad work to balance)
123
since moment arm of the trunk weight increases with increases knee flexion, what happens to the quadfs
must increase work to balance
124
when standing starightm the moment arm is where
middle of the knee
125
understand slide about closed kinetic chain squatting and the impact on the moment arm of the trunk wwight (and what quads have to do)
since moment arm of trunk weight increaes with flexion, this increases the moment.
Quads must create extension moment to counteract body weight (must increase work to balance forces)
126
what happens to moment arm of the ankle weight and leg with knee extension (open kinetic chain)
moment arm of ankle weight and leg increases as knee extends, icnreases flexion moment
=more quadriceps work (extension moment to balance)
127
in open kinetic chain, is the moment arm longer in knee flexion or extension
knee extension
128
in flexion, moment arm between weight of ankle and knee will icnrease or decrease and what does that do to quads
it will decrease therefore quadricep force and work will decrease
129
in full extnesion of knee, what happens with moment arm and quad work
there is the longest moment arm between weight or ankle and knees therefore there is an increased flexion moment, the quads must increase force to balance
130
what type of bone is the opatella
sesmoid bone
131
where is the patella located
knee
imbedded on quad tendon
132
what is the functin of the patella
increase the moment arm of the quads tendon (increase effectiveness of quads)
protect quadriceps tendon from excessive frcition from the femur
133
explain the effect of patella on moment arm
the patella lengthens the level arm, therefore to do the same moment, the quads will have to work less
134
what are the 2 lines of the q angle
line 1: ASIS to patella centre
line 2: tibial tubercle to patella centre
135
what is the Q angle
angle between lines 1 and 2
136
what is the normal q angle for men and women
13 for men
18 for women
137
what are you at risk for with increased Q angle
increased risk of anterior knee pain (patellofemoral pain syndrome) and lateral patella dislocation
138
there is an increased risk of anterior knee pain (patellofemoral pain syndrome) and lateral patella dislocation with an increased or decreased Q angle
increased
139
what does the q angle represent
lateral pull of quadriceps on patella
(incrase Q angle = incrase latearl pull)
140
increase q angle increases medial or lateral pull
lateral pull
141
what is the protection against an icnreased Q angle
lateral femoral condyle (larger anterior)
medial extensor retinaculum
vastus medialis
142
how does the patella move during knee flexion
patella glides inferior during knee flexion
(more contact between patella and femur)
143
is there more contact between patella and femur during flexion or etension of the knee
flexion
144
during full knee extension, there is minimal or maximal contact between patella and femur
minimal
145
as patella slides inferior, thjere is an BLANK contact with femur
increase
146
does the superior or interior aspect of the patella get more contact points
increased contact points as you move superiorly
147
greater knee felxion, the more the patella is pulled where
more the patella is pulled towards the femur
148
explain the different in patella joint forces beetween 5 degrees and 70 degreses knee flexion
at 5 degrees, the quad is pulling more vertically (less joint reaction force)
at 70 degrees, the quad is pulling more posterioly against the femur and increases the joint raction forces
149
explain the patella joint reaction force during free weight with increases knee felxion angle
initially, in full extension, there is low contact between patella and femur
As you increased flexion, there is an increase posterior pull of patella on femur which increases the joint reaction forces
at the end, with increased flexion, the moment arm of the ankle decreases alot therefore decrases the patella joint reaciton forces
150
explain the patella joint reaction force during squat (CKC) with increases knee felxion angle
1) with increasing flexion, there is an increased posterior pull on the patella (increasing patella joint reaction forces)
2) As you squat, body weight moves posteriorly and that icnreases the moment arm and moment
this means an increased force of quads needed to maintain upright which incrases patella joint recation forces
151
be able to interpret patella joint reaction forces
