Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Unit 3 Biomechanics Winter 2024 > Knee region > Flashcards

Knee region Flashcards

1
Q

What is normal genu valgus?

A
  • 170-175 degrees
  • the angle the femur and tibia make in relation to the outside of the leg
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is excessive genu valgus?

A
  • less than 170 degrees (knock knee)
  • leads to hip adduction and ankle pronation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is genu varum?

A
  • greater than 180 degrees (bow legged)
  • leads to hip abduction and ankle supination
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are all the tissues that connect to the medial meniscus?

A
  • MCL
  • coronary ligaments
  • quads
  • semimembranosus
  • medial joint capsule
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are all the tissues that connect to the lateral meniscus?

A
  • popliteus
  • coronary ligaments
  • quads
  • semimembranosus
  • lateral joint capsule
  • posterior meniscofemoral ligament
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the main functions of the menisci?

A
  • decrease compression
  • stabilize joint
  • lubricate cartilage
  • proprioception
  • guide arthrokinematics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why can’t the menisci heal very well?

A
  • only vascularized on outer 1/3rd
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Which meniscus is more frequently injured?

A
  • medial meniscus
  • has more attachments so doesn’t move as freely as lateral one
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why would active hamstring strengthening after a fresh meniscal surgery potentially be detrimental to the tissue?

A
  • semimembranosus attaches to BOTH menisci so a fresh repair could be torn with hamstring activation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is knee rotation named?

A
  • axial rotation by tibial tuberosity relative to distal anterior femur
  • tibial-on-femoral ER: tibia ER’s on fixed femur
  • femoral-on-tibial ER: femur IR’s on fixed tibia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the arthrokinematics of tibial-on-femoral knee extension

A

Concave tibia rolls and slides anterior

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the arthrokinematics of tibial-on-femoral knee flexion

A

concave tibia rolls and slides posterior

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the arthrokinematics of femoral-on-tibial knee extension

A

convex femur rolls anterior and slides posterior

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the arthrokinematics of femoral-on-tibial knee flexion

A

convex fmeur rolls posterior and slides anterior

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the Screw-Home mechanism of the knee?

A
  • obligatory ER of the tibia of about 10 degrees in the last 30 degrees of knee extension
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the movement that occurs in the last 10 degrees of knee extension

A
  • the tibial tubercle moves into alignment with the lateral femoral condyle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What factors cause the Screw-Home mechanism?

A
  • shape of the medial femoral condyle
  • passive tension in ACL
  • slight lateral pull of quads
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the primary guiding mechanism for the screw home movement of the knee?

A
  • medial condyle shape
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How does the knee get out of the Screw-Home position?

A
  • popliteus “unlocks” the knee to IR for flexion from fully extended position
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

If the foot is planted and a valgus force is applied to the knee, what structures could be damaged?

A
  • MCL
  • Posterior medial capsule (PMC)
  • ACL
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What injury is the MCL most vulnerable to?

A
  • closed chain + full EXT + valgus force + extreme ER
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What do the MCL and LCL resist?

A
  • MCL: resists valgus
  • LCL: resists varus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What knee ROM makes the ACL most taut?

A
  • posterior lateral bundle is full extension
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What affect does quad activation have on the ACL & in what ROM?

A
  • during last 50-60 degrees of knee extension they pull tibia anteriorly
  • causes ACL to become taut
  • quads are the ACL’s antagonist
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What knee motion makes the PCL most taut?

A
  • knee flexion
  • peak at 90-120 degrees
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What affect does hamstring activation have on the PCL & in what ROM?

A
  • hamstrings are the PCL’s antagonist
  • pulls it taut in about 90-120 degrees of knee flexion
27
Q

What is the most common mechanism of injury for the PCL?

A
  • high-injury trauma
  • falling on the knee or car crash (“dashboard” injury)
28
Q

How is the patellofemoral joint stabilized?

A
  • quads
  • articular fit
  • surrounding soft tissue
29
Q

In which position is the patella least stable?

A
  • full extension w/ quads relaxed
30
Q

How does the patella move during knee flexion & extension?

A

T-on-F:
- flex: patella slides inferior
- ext: patella slides superior

F-on-T:
- trochlear groove slides beneath patella

31
Q

When in the ROM does each part of the patella contact the trochlear groove?

A

135 flex: facets contact groove
90 flex: superior pole
60-90 flex: most contact area
20-30 flex: inferior pole
0 flex: contacts suprapatellar fat pad

32
Q

What structures make up the knee extensor mechanism?

A
  • quads
  • quad tendon
  • patella
33
Q

When in the ROM are quad torques largest for open chain knee extension?

A
  • 45-70 degrees knee flexion
34
Q

When in the ROM are quad torques largest for closed chain knee extension?

A
  • 90-45 degrees knee flexion
35
Q

How does the patella enhance quad function?

A
  • increases IMA of knee extensor mechanism
  • increases greatest amount of torque we can produce
36
Q

What are the 3 factors influencing the moment arm of the knee extensor mechanism?

A
  • shape and position of patella
  • shape of distal femur
  • migrating AoR
37
Q

What affect does quad stress have on different impairments?

A

Damages w/:
- patellofemoral pain
- OA

Therapeutic w/:
- healthy
- late phase ACL rehab

38
Q

Why does extensor lag occur?

A
  • weakness of quads that fails to full extend the knee
  • usually after surgery or trauma to knee
  • swelling increases intra-articular pressure which inhibits neural activation of quads
39
Q

Why does PFJ compression increase with deeper squatting?

A
  • deep squats decreases the angle of pull of the quads which increases magnitude of force directed into the trochlear groove
40
Q

What are some local factors that could cause patella mal-tracking in the trochlear groove?

A

Lateral bowstringing
- ITB or lateral patellar retinacular tightness

flatten lateral trochlear groove
patella alta (high patella)
atrophied VMO (w/ rest of quads)
ruptured medial patellar retinacular fibers

41
Q

What are some global factors that could cause patella mal-tracking in the trochlear groove?

A

Excessive genu valgum
- weak hip abductors
- tight hip adductors

Excessive knee ER
- weak hip ER’s + abductors
- tight hip IR’s + adductors

42
Q

When during knee ROM do the hamstrings have the best leverage?

A

50-90 degrees knee flexion

43
Q

When during knee ROM do the hamstrings generate the best torque?

A

20 degrees knee flexion

44
Q

Why are the hamstrings best leverage position different from their greatest torque position?

A
  • the length-tension relationship is essential when looking at torque potential
  • it is optimal when lengthened (20 degrees knee flexion)
45
Q

What is the active and passive insufficiency for the quads?

A

Active:
- hip flexion + knee extension

Passive:
- hip extension + knee flexion

46
Q

What is the active and passive insufficiency for the hamstrings?

A

Active:
- hip extension + knee flexion

Passive:
- hip flexion + knee extension

47
Q

What are some detrimental effects of Genu Varum?

A
  • increases medial joint loading -> greater loss of joint space -> greater knee adduction -> increased strain on LCL
48
Q

What are some detrimental effects of Genu Valgum?

A
  • MCL + medial capsule stress
  • patellar maltracking
  • ACL stress
  • lateral compartment OA leading to knee replacement
49
Q

What are some potential causes of Genu Valgum?

A
  • previous injury
  • high BMI
  • ligament laxity
  • weak hip abductors
  • excessive foot pronation
50
Q

What are some detrimental effects of Genu Recurvatum?

A

10 degrees extended beyond neutral
- posterior structure laxity
- altered arthrokinematics while walking/weight bearing

51
Q

What is jumper’s knee?

A
  • patellar tendinopathy
  • chronic pain in patellar ligament/tendon
52
Q

Why does jumpers knee occur?

A
  • overuse & wear
  • Extrinsic: training intensity, playing surface/footwear
  • Intrinsic: strength, endurance, flexibility, skill level, BW + height, male
53
Q

What is patellofemoral pain syndrome?

A
  • pain behind patella & anterior to femur
  • usually worse w/ squatting, stair climbing, prolonged sitting w/ knee flexed
54
Q

What are some causes of patellofemoral pain syndrome?

A
  • neurological, genetic, neuromuscular

Biomechanical
- stress intolerance of articular cartilage & subchondral bone
- abnormal tracking & alignment of patella in trochlear groove

55
Q

How would you instruct someone to squat who had patellofemoral pain syndrome?

A
  • restrict ROM on a squat
  • don’t deep squat and keep knees behind toes (this shifts IMA of quads and increases IMA of hip extensors)
  • don’t allow knees to collapse and don’t stress quads too much
56
Q

What is the mechanism of injury for meniscal tears?

A
  • forceful, axial rotation of femoral condyles over a flexed & weight bearing knee
  • pinches and dislodges meniscus
57
Q

What are potential consequences of a partial meniscectomy?

A
  • less coverage & shock absorption for articular cartilage ALL leads to OA
58
Q

What is the mechanism of injury for an ACL injury?

A
  • non-contact
  • strong quad contraction over slightly flexed knee
  • valgus collapse
  • excessive ER + planted foot
  • knee IR + EXT + valgus
  • hyperextension + planted foot
59
Q

What are some related injuries to an ACL injury?

A
  • cartilage degeneration
  • menisci degeneration
  • MCL tear/rupture
60
Q

What is the terrible triad?

A
  • MCL tear
  • ACL tear
  • Medial meniscus tear
61
Q

Why are female athletes more likely to tear an ACL than male athletes?

A
  • tend to land w/ knees in greater valgus alignment
  • land with less trunk, hip, & knee flexion
  • quad dominant landing
  • pulls tibia anterior & strains ACL
62
Q

How would you choose to strengthen the quads after an ACL surgery & why?

A
  • close chained quad training (leg press, squats)

ACL strain greatest w/ isolated quad contraction in last 30-40 degrees of extension
- limit ROM and don’t do open-chain knee extension in early stages

63
Q

What are the AAOS norms for knee flexion and extension?

A

Flex: 135

Ext: 10

Unit 3 Biomechanics Winter 2024 (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions