Lecture 8 - Biomechanics of the Knee (part 1) Flashcards
1
Q
What are the 2 joints of the knee?
A
tibiofemoral and patellofemoral
2
Q
What 3 bones comprises the knee?
A
- femur (distal) (medial + lateral condyle)
- tibia (proximal)
- patella
3
Q
Which condyles of the femur articular with the tibia?
A
the medial and lateral condyles
4
Q
Which condyle is bigger?
A
the medial condyle
5
Q
What surface articulates with the patella?
A
the patellar surface
6
Q
What surface prevents lateral patella dislocation?
A
the patellar surface
7
Q
What kind of slope does the tibial plateau have?
A
posterior
8
Q
What kind of area does the medial tibial plateau have?
A
large
9
Q
What kind of shape is the medial tibial plateau?
A
concave but relatively flat
10
Q
What kind of shape is the lateral tibial plateau?
A
concave in medial-lateral direction, flatter than medial plateau
11
Q
Which bone is the largest sesamoid?
A
the patella
12
Q
What are the 3 functions of the patella?
A
- Protects quadriceps from excessive friction
during knee flexion - Increases angle of application of quadriceps
- Increases moment arm of the quadriceps tendon
13
Q
What would happen if the patella was removed?
A
can reduce the quadriceps moment arm by 33-70% with the knee extended and the moment generated by the muscle may be reduced up to 40%
14
Q
Which 3 bones demonstrate trabecular bone organization?
A
distal femur, proximal tibia, and patella
15
Q
Which cartilage is the thickest in the body?
A
articular cartilage
16
Q
The articular cartilage helps improve congruity between which 2 joints’ articulating surfaces?
A
the patellofemoral and tibiofemoral joints
17
Q
What does the articular cartilage increase?
A
area of contact
18
Q
What are the 4 noncontractile supporting structures?
A
- Articularcapsule
- Collateralligaments
- Cruciateligaments
- Accessoryligaments
19
Q
What are the 4 articular structures of the knee?
A
- trabecular bone
- articular cartilage
- menisci
- noncontractile supporting structures
20
Q
What shape of the fibrocartilage discs?
A
wedged
21
Q
Where are fibrocartilage discs located?
A
between the femur and tibia
22
Q
What blood supply is found in the fibrocartilage disks?
A
peripheral blood supply
23
Q
What are the 3 functions of the menisci?
A
- Enhancejointlubrication
- Protect underlying articular cartilage
- Increase contact area between tibia and femur (~doubles the surface contact area) and thus decreases stress
24
Q
What are the 2 collateral ligaments?
A
medial and lateral
25
What does the MCL stabilize against?
valgus directed
(abductor) force
26
Which collateral ligament is most commonly injured?
MCL
27
What does the LCL stabilize against?
varus directed (adductor) force
28
What are the 2 cruciate ligaments?
anterior and posterior
29
What does the ACL resist?
anterior glide of tibia
30
What does the ACL limit?
extension ROM with menisci
31
What kind of stabilization does the ACL have?
frontal and transverse plane stabilization
32
What does the PCL resist?
posterior glide of tibia, rotation, varus and valgus
33
What stabilization does the PCL have?
frontal and transverse plane stabilization
34
What rotation does the PCL limit?
lateral tibial rotation with LCL
35
What are the 2 flexors of the knee?
hamstrings and popliteus
36
What are the 3 medial rotators of the knee?
sartorius, gracilis, pes anserinus
37
What are the 4 extensors of the knee?
rectus femoris, vestus intermedius/lateralis/medialis
38
What is the lateral rotator of the knee?
tensor fasciae latae
39
What is the alignment of the knee joint affected by?
* Foot, ankle, and hip alignment
* Muscle imbalances
* Abnormal loads on joint
40
What are the 2 frontal plane alignments of the knee joint?
varus and valgrus
41
What is the saggital plane alignment of the knee joint?
180 degrees
42
What is the transverse plane alignment of the knee joint?
0 degrees
43
What is varus sometimes referred to?
bow leg
44
Where is the line found in varus cases?
between proximal and distal joints passes medial to the center of the knee
45
Where does varus increase force across?
the medial tibiofemoral compartment
46
Where is the line found in valgus cases?
between proximal and distal joints and passes lateral to the center of the knee
47
Where does valgus increase fore across?
lateral tibiofemoral compartment
48
What is valgus sometimes referred to?
knock-knee
49
Where is the mechanical axis found?
femoral head to ankle
50
Where is the anatomical axis found?
femoral head to knee
51
What are the 2 axes of the lower limb?
mechanical and anatomical axis
52
What knee alignment can newborns/young children exhibit?
genu varum
53
What is genu varum?
varus alignment that goes away by 3-4 years of age
54
What is genu recurvatum?
knee hyperextension
55
What does genu recurvatum result from?
muscle imbalances at the ankle or knee
56
What does genu recurvatum apply increased stress to?
ACL and posterior knee structures
57
Which two structures are aligned so tranverse axes of proximal tibia and distal femur are parallel in knee extension?
tibial plateaus and femoral condyles
58
What is knee OA equal to?
5 degrees tibial version
59
How many lines make up the Q-angle?
2
60
Where is line 1 of the Q-angle?
ASIS to patella center
61
Where is line 2 of the Q-angle?
tibial tubercle to patella center
62
Increased Q angle is considered a risk factor for...
* Patellofemoral pain (PFP)
* Patellar subluxation and dislocation
* Knee OA
* Overuse injuries, etc.
63
What increases with the Q angle?
the lateral pull of quadriceps on patella
64
What is the stability of the lateral pull of quadriceps on patella enhanced by?
- lateral femoral condyle
- medial extensor retinaculum
- vastus medialis
65
How many degrees of freedom does the knee have?
6
66
What plane is the normal ROM of the knee?
saggital
67
What does ROM change with?
age
68
What is uncommon with ROM?
hyperextension ROM
69
What are the 2 kinetic chains?
closed and open
70
What does movement of one joint cause in a closed chain?
causes the other joints in the chain to move in a predictable manner
71
What is an example of a closed chain?
rising from a chair or doing a push up
72
What does movement of one joint cause in an open chain?
it is independent of other joints in the chain
73
What is an example of an open chain?
swing phase of gait or bicep curls
74
In a closed chain, the segment furthest from the body is ___.
fixed/stationary
75
In an open chain, the segment furthest from the body is ___ and ___ fixed to an object.
free, not
76
What does moment arm of the trunk weight increase with?
increasing knee flexion
77
What makes pure rolling motion of the tibiofemoral joint possible?
the more articular surface on the femoral side of the knee joint
78
What is pure rolling?
every point of contact on one surface has a unique point of contact on other surface
79
What does the relative motion between the tibia and femur depend on?
which parts are in contact
80
What two surface shapes directly impact the relative motion of the tibiofemoral joint?
the femoral and tibial articular surface shapes
81
What surfaces contribute to 3-D movement of the femur and tibia during knee flexion and extension?
tibiofemoral joint surfaces
82
What does the tibiofemoral motion not adhere strictly to?
the concave-convex rule
83
When a convex joint surface is moving, roll and glide occurs in the ___ direction; when a concave joint surface is moving, the roll and glide occurs in the ___ direction.
opposite, same
84
When is the rate of rotation the greatest?
at the end of extension between 30 degrees of flexion and complete extension
85
During flexion, as the femur rolls into ___, it rotates ___ with respect to the tibia.
flexion, laterally
86
The femur rotates ___ as it rolls into extension.
medially
87
Contact between the femur and tibia migrates...
* Posteriorly on the tibia during flexion
* Anteriorly on the tibia during extension
88
Posterior translation of the femur on the tibia during ___.
flexion
89
Anterior translation of the femur on the tibia during ___.
extension
90
What does the patellofemoral motion depend on?
knee position
91
In extension, the patella is ___.
moveable
92
Translation of the patella during knee flexion is ___ cm distal glide with knee flexion.
5-7
93
What action does the patella do during knee flexion?
rotates and tilts laterally until at least 90 degrees of knee flexion
94
What happens during contact ACL injuries?
* Footplanted
* Femur driven posterior
* Rotation
95
What happens during non-contact ACL injuries?
* Landing, deceleration, pivoting/cutting
* Knee/hip in extension+valgus
* Quadriceps overload
