Knee Biomechanics Flashcards
(172 cards)
1
Q
What is the size of the posterior tibial slope
A
9 degrees inferiorly
2
Q
What is the closed pack position of the knee
A
Extension
3
Q
What is the normal range of knee flexion with hip flexion
A
130-140
4
Q
What is the normal knee flexion with hip extension
A
120
5
Q
What is the only quadriceps muscle to cross the hip
A
Rectus femoris
6
Q
How much knee flexion is needed for level surface gait
A
60-68
7
Q
How much knee flexion is needed for ascending stairs
A
80
8
Q
How much knee flexion is needed for descending stairs
A
90
9
Q
How much knee flexion is needed for sit stand sit transfer
A
90
10
Q
How much knee flexion is needed to tie a shoe
A
106
11
Q
How much knee flexion is needed for full squat to floor
A
150-160
12
Q
What is normal range of knee extension
A
5-10 hyperextension
13
Q
What is the AAOS normal range for knee flexion
A
10-0-135
14
Q
Which meniscal horn tears are more effected while descending stairs
A
Posterior horns
15
Q
Which meniscal horn tears are more effected while ascending stairs
A
Anterior horns
16
Q
How can your knee flex to 150-160 during a deep squat if the normal range is 135
A
Due to the super incumbent body weight
17
Q
Are the femoral condyles concave or convex
A
Convex
18
Q
Is the tibial plateau concave or convex
A
Concave
19
Q
Which side of the tibial plateau is more concave and which is flat/slightly convex
A
Lateral is flat/slightly convex
Medial is more concave
20
Q
What are the arthrokinematics of OKC knee extension
A
Concave tibial plateau moving on convex femoral condyles
21
Q
Which way do the mensci translate during OKC knee motions
A
The same direction of the roll
22
Q
Which way if the patella drawn during OKC knee extension
A
Superiorly
23
Q
What does the patella moving superiorly do to the menisci
A
Pulls them anteriorl
24
Q
How does the patella pull the menisci anteriorly
A
Due to the attachment of the coronary ligaments from patella to the anterior horns of the mensci
25
Which way are the menisci drawn during OKC knee flexon
Posteriorly
26
What cause the menisci to be drawn posteriorly during OKC knee flexion
Attachment of the semimebranosus and popliteus to the posterior horns of the menisci
27
Which menisci do the semimembranosus and popliteus attache to
Semimembranosus: medial meniscus
Popliteus: lateral meniscus
28
What is the function of the popliteus
Initiate flexion of the knee
29
What does the popliteus act like
Anconeus
30
What are the functions of the menisci (3)
1. Increases tibial plateau radius of curvature
2. Reduces tibiofemoral friction
3. Attenuates tibiofemoral compression loads
31
How much of the menisci are red zone and white zone
Red: 1/3
White: 2/3
32
Which compartment of the knee has more surface area
Medial compartment
33
What are the arthrokinematics of CKC knee flexion
Convex femur on concave tibia
34
What is the roll and slide with CKC knee flexion
Posterior roll and anterior glide
35
What happens at 15 degrees of knee flexion
Medial compartment posterior roll begins to be accompanied by a small amount of anterior slide
36
Why is there anterior slide on the medial compartment during knee flexion at 15 degrees
Due to the larger surface area resulting in more ground to cover
37
How do you name rotation of the knee
Based on the tibia
38
What type of knee rotation occurs with CKC knee flexion
Internal rotation
39
What type of knee rotation occurs with CKC knee extension
External rotation
40
What happens at 25 degrees of CKC knee flexion
Lateral compartment posterior roll begins to be accompanied by anterior glide
41
What happens at mid ROM CKC knee flexion
Equal amounts of posterior roll and anterior glide in both compartments
42
What happens at late ROM CKC knee flexion
Greater anterior glide than posterior roll in both compartments
43
What happens at end ROM CKC knee flexion
All anterior femoral glide in both compartments
44
When is the angle of inclination of the ACL the greatest
Full knee extension
45
What is the main function of the ACL
Convert roll into slide
46
What happens to the inclination of the ACL as knee flexion increases
Decreases
47
Is the ACL in a better position to create anterior glide of the femur on the tibia in full knee extension or knee flexion and why
Knee flexion due to decreased angle of inclination
48
What position is the ACL most vulnerable to being torn full knee extension or knee flexion
Knee flexion
49
What happens to the ACL at end ROM extension
The midsubstance of the ACL comes in contact with the femoral intercondylar shelf
50
What is another name for the intercondylar shelf
Notch of Grant
51
What does the contact point with the notch of Grant do to the ACL
Acts as a fulcrum to tension load the ACL
52
True or False:
| Constant rubbing of the ACL on the notch of Grant can lead to an ACL tear
True
53
Where does the ACL insert on the femur
Medial aspect of lateral femoral condyle
54
Where does the ACL run
Anteromedial to posterolateral
55
Do we want ligaments to have small or large angles of inclination
Small angles of inclination
56
What are the 2 bands of the ACL
1. Anteromedial band (AMB)
| 2. Posterolateral band (PLB)
57
When is the AMB of the ACL most taut
Greater degrees of flexion
58
When is the PLB of the ACL most taut
Greater degrees of extension
59
What is isometricity
Some portion of a ligament is taut in all varying degrees of osteokinematic motion
60
True or False:
| The ACL has isometricity
True
61
At what amount of knee flexion are both bands of the ACL not particularly tensed
30 degrees
62
What is the lack of tension at 30 degrees good for
Testing the integrity of the ACL
63
Why is there great tension in both bands of the ACL during hyperextension of the knee
The ACL is hitting the Notch of Grant
64
When is the angle of inclination of the PCL the greatest
Full flexion
65
Where does the PCL insert on the femur
Lateral aspect of medial femoral condyle
66
Where does the PCL run
Posterolateral to anteromedial
67
How many bundles does the PCL have
2
68
Do the bundles of the PCL have different or the same function
Same
69
What happens to the angle of inclination of the PCL during knee extension
Decreases
70
What is the function of the PCL
Convert anterior roll of the femur into posterior glide of the femur
71
What does the ACL prevent in the OKC
Anterior translation of the tibia on the femur
72
What does the ACL prevent in the CKC
Posterior translation of the femur on the tibia
73
What does the PCL prevent in the OKC
Posterior translation of the tibia on the femur
74
What does the PCL prevent in the CKC
Anterior translation of the femur on the tibia
75
Are transverse plane motions at the knee passive or active motions
Passive only
76
How much lateral/external rotation occurs at the knee at 90 degrees of knee flexion
40
77
How much medial/internal rotation occurs at the knee at 90 degrees of knee flexion
30
78
Does the amount of knee rotation increase or decrease with greater knee flexion/extension
Decreases
79
Where does the longitudinal axis run for the knee
Medial to the medial tibial intercondylar tubercle
80
What does the location of the longitudinal axis of the knee result in
Greater excursion laterally than medially during rotation
81
What check rein IR of the knee
The cruciates
82
What check rein ER of the knee
The collaterals
83
Do the cruciates physically wind around each other
Yes
84
Do the collaterals physically wind around each other
No the wind around one another in space
85
What motions tear the collaterals more often and why
Varus and valgus motions due to the ligaments being in the frontal plane
86
What plane does the lateral femoral condyle lie in
Sagittal plane
87
Which condyle of the femur has a large A-P dimension
Lateral femoral condyle
88
What does the greater amount of A-P dimension of the lateral condyle provide
Buttress for the patella to help prevent lateral dislocations
89
What plane does the medial femoral condyle lie in
Oblique to the sagittal plane
90
What femoral condyle has greater surface area
Medial femoral condyle
91
What is the screw home mechanism of the knee
Obligatory ER of the tibia with terminal 20-30 degrees of knee extension
92
What is a negative Helfet test
ER of the tibia in knee extension
93
What are the 2 things that contribute to the screw home mechanism
1. Femoral condyle surface area contribution
| 2. Cruciate contribution
94
What type of ACL/PCL tears would you not see a positive Helfet test
Grade 1 because there is no tearing of fibers
95
What is a positive Helfet test
No ER of the tibia in knee extension
96
What does a positive Helfet test look like
Tibial tuberosity and patella are still in line with one another during knee extension
97
What type of ACL/PCL tears are you able to see a positive Helfet test
Grade 2 and 3
98
What contributes more to the screw home mechanism of the knee the femoral condyle surface area or the cruciate ligaments
Cruciate ligaments
99
How do the ACL and PCL contribute to the screw home mechanism during knee extension
During extension the ACL and PCL wind up on each other becoming tighter and they unwind to relieve some of the tension
100
What is the order of motions at the knee that effect the next
Sagittal plane motion creates transverse plane motion which creates frontal plane motion
101
What is the anatomic or longitudinal axis of the tibiofemoral joint
5-10 degrees of physiologic valgus
102
What creates the physiologic valgus of the knee (2)
1. Coxa varum
| 2. Medial femoral condyle projects more distal
103
Which component of the physiologic valgus occurs distally
Medial femoral condyle projects more distal
104
Which component of the physiologic valgus occurs proximally
Coxa varum or proximal femoral angle of inclination
105
Where does the mechanical axis of the tibiofemoral joint run
The weight bearing line from the center of the femoral head to superior talus center
106
What does the mechanical axis of the tibiofemoral joint allow for
Equal weight bearing in stance of the medial and lateral tibiofemoral compartments
107
Ideally where should the hip joint fall in relation to the knee joint
Directly over the middle of the knee
108
What does increased valgus at the knee result in (3)
1. Compression overload to the lateral tibiofemoral compartment
2. Distraction overload to medial tibiofemoral compartment
3. Tension load soft tissue on medial side
109
What does decrease valgus/increased varum at the knee result in (3)
1. Compression overload to the medial tibiofemoral compartment
2. Distraction overload to the lateral tibiofemoral compartment
3. Tension load soft tissue on the lateral side
110
With IR of the knee what occurs slight valgus or varus
Slight valgus
111
With ER of the knee what occurs slight valgus or varum
Slight varum
112
What causes the slight valgus/varum during IR and ER of the knee
The 9 degree inferior and posterior slope of the tibial plateau
113
If the femoral condyle sits on the posterior plateau it is considered shorter or longer
Shorter
114
If the femoral condyle sits on the anterior plateau it is considered shorter or longer
Longer
115
What happens to the lateral femoral condyle during ER of the knee
Climbs up the tibial plateau slope lengthening the lateral compartment
116
What happens to the medial femoral condyle during ER of the knee
Falls down the tibial plateau slope shortening the medial compartment
117
What happens during OKC ER to the knee in the frontal plane
Lengthened lateral compartment, shortened medial compartment resulting in tibiofemoral varus
118
What happens during CKC ER to the knee in the frontal plane
Lengthened lateral compartment, shortened medial compartment resulting in tibiofemoral varus
119
What happens during OKC IR to the knee in the frontal plane
Shortened lateral compartment, lengthened medial compartment resulting in tibiofemoral valgus
120
What happens during CKC IR to the knee in the frontal plane
Shortened lateral compartment, lengthened medial compartment resulting in tibiofemoral valgus
121
How much does the patella increase the MA of the quadriceps at 0 extension
31%
122
How much does the patella increase the MA of the quadriceps at 90 flexion
13%
123
Why does the patella not need to increase the MA of the quadriceps as much at 90 of flexion compared to 0 extension
The length tension relationship of the quadriceps is more optimal at 90 flexion
124
At what angle is the length tension relationship of the quadriceps the most optimal
60 flexion
125
What happens to the compressive force if there is no patella
There is no compressive force
126
Which way do most patellar dislocations occur
Laterally
127
What is the equation for torque
T=FxD or MA
128
Someone with a patellectomy will present with what
Extensor lag
129
What does the compressive force do to the patella
Stabilizes the patella in trochlea groove
130
True or False:
| The patella assures some compression in full extension
True
131
Is the patella in the femoral sulcus in full extension or hyperextension
Nope
132
What do we need to ensure stability of the patella during full extension or hyperextension
A compressive force
133
Does the patella have an increased or decreased chance for dislocation in full extension or hyperextension
Increased risk
134
What does it mean if you palpate the patella and it moves
The patient is not firing their quads therefore the line of gravity falls anterior the the axis of rotation creating an extension moment
135
What happens to e patellofemoral compression (PFC) as flexion increases
PFC increases
136
How much compression does the patella experience during gait
0.5 x BW
137
How much compression does the patella experience while ascending/descending stairs
3.4 x BW
138
How much compression does the patella experience while squatting
8.8 x BW
139
Where is the thickest amount of hyaline cartilage and the thickness of it
Retropatellar 5mm
140
What happens to the patella from 90 to 120 of flexion that allows for compression to decrease a bit
Tilts a bit
141
What happens to patellofemoral contact area as you increase knee flexion
Contact area increases
142
When does the patella start to contact the femur
About 20 flexion
143
When is patellofemoral contact the greatest
About 90 flexion
144
When does the inferior facet of the patella contact the femur
20 knee flexion
145
When does the middle facet of the patella contact the femur
45 knee flexion
146
When does the superior facet of the patella contact the femur
90 knee flexion
147
When does the medial/odd facet of the patella contact the femur
120 knee flexion
148
When does the lateral facet of the patella contact the femur
From 20 knee flexion on
149
As a person why is common to have pain on the medial side of the patella when squatting
Wolff's Law, older people don't spend too much time in the squatted position so the cartilage on the medial side of the patella becomes soft and doesn't absorb compressive loads as well
150
The patella has what shape of motion when it drops down into the sulcus as knee flexion occurs
C or J shape
151
What is the normal length of the patellar ligament compared to the patella
1:1 the patellar ligament length should be the same as the patella height
152
What is patella baja
Patellar ligament is too small
153
What does patella baja result in
The inferior facet of the patella contacting the femur sooner which can lead to DJD over time due to increased compression
154
What is patella alta
Patellar ligament is too long
155
What does patella alta result in (2)
1. Inferior facet of the patella contacts femur later leading to chondromalacia patella due to decreased compression
2. More susceptible to patellar subluxation/dislocation
156
Why does patella alta result in an increased susceptibility to patellar subluxation/dislocation
The patella is not in contact with another bone for a longer amount of time and there is less of a barrier on both sides of the patella
157
What is one way a person can get patella baja
ACL reconstruction with patellar graft
158
Is patella alta acquired or congenital
Congenital very rarely acquired
159
What does the patella do for the quadriceps
Acts as a link to focus the divergent pull of the 4 individual quads onto one singular point at the tibial tubercle
160
How does the ITB impact the patella in the frontal plane
It adds an additional force with the tendency to laterally or superiorly translate the patella
161
Where does the ITB insert at the knee (2)
1. Gerdy's tubercle
| 2. Lateral side of the patella
162
What can a tight ITB band result in
Lateral subluxation/dislocation of the patella
163
How do you measure the Q angle
ASIS to mid point of the patella and tibial tuberosity to mid point of patella and measure the angle
164
What is the normal Q angle for men and women
Men: 13
Women: 18
165
What does the resultant force of the Q angle have a tendency to do
Laterally translate the patella
166
What are the biomechanics that increase the Q angle (3)
1. Laterally displace tibial tubercle
2. Medially displace patella
3. Laterally displace ASIS
167
What are the 2 ways to laterally displace the tibial tubercle
1. External tibial rotation
| 2. External tibial torsion
168
What are the 2 ways to medially displace the patella
1. Internal femoral rotation
| 2. Femoral anteversion
169
Who has a more laterally displaced ASIS men or women
Women due to larger pelvis for birth purposes
170
When does subluxation/dislocation of the patella occur (5)
1. Greatest Q angle
2. Least patellofemoral compression
3. Greatest quad force
4. Least patellar contact with femoral trochlea
5. Full extension or hyperextension
171
What causes the greatest quad force (2)
1. Smallest quad moment arm
| 2. Poor length tension relationship
172
Why does full extension or hyperextension increase the risk of subluxation/dislocation
There is no contact with the femoral trochlea
