Lecture 9 - Biomechanics of the Knee (part 2) Flashcards

1
Q

What are the main knee extensors?

A

Quadriceps femoris:
- rectus femoris
- vastus intermedius
- vastus lateralis
- vastus medialis

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

What kind of muscle is the rectus femoris?

A

multi-joint muscle

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

What effects of weakness does the rectus femoris have?

A

reduction in hip flexion/knee extension strength

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

What kind of joint knee extensor is the vastus intermedius?

A

single joint knee extensor

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

What effect of weakness does the vastus intermedius have?

A

decreased knee ext. strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What effect of tightness does the vastus intermedius have?

A

decreased knee flexion ROM

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which is the largest of the quad muscles?

A

vastus lateralis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the dominant knee extensor?

A

vastus lateralis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the effect of weakness in the vastus lateralis?

A

reduced knee extension strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the effect of weakness in the vastus lateralis?

A

limits knee flexion ROM

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What % of knee extensor torque does the vastus medialis have?

A

10-12%

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

What does the vastus medialis balance?

A

the pull of the heads of the quads

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

What two knee extensors pull along the femur?

A

RF and VI

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

What knee extensor pulls lateral quad?

A

VL

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

Which muscle can balance with a medial pull?

A

only VM

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the effect of weakness in the vastus medialis?

A

lateral shift in patellar movement

17
Q

What is the effect of tightness in the vastus medialis?

A

contributes to decreased knee flexion ROM

18
Q

Strength in what muscle may protect knee joint degeneration?

A

quadriceps femoris

19
Q

What are the 5 main knee flexors?

A

hamstrings
popliteus
gracilis
sartorius
gastrocnemius

20
Q

What are the 4 muscles part of the hamstrings?

A
  • Bicep femoris longus (long head)
  • Bicep femoris brevis (short head)
  • Semitendinosus
  • Semimembranosus
21
Q

Which muscle of the hamstrings is the smallest but has the largest moment arm?

A

semitendinosus

22
Q

Which muscle of the hamstrings is the largest?

A

semimembranosus

23
Q

What do the hamstrings contribute to?

A
  • medial/lateral rotation
  • hip extension (not BF brevis)
  • knee stability
24
Q

What are the 2 effects of weakness in the hamstrings?

A
  • Loss of knee flexion strength
  • Produces little disability (control of knee flexion in everyday activities usually by eccentric contraction of quads)
25
What are the effects of tightness in the hamstrings?
* Limits knee extension ROM (hip flexed) * Limit hip flexion ROM (knee extended)
26
What are the 5 main knee medial rotators?
- sartorius - gracilis - semitendinosus - semimembranosus - popliteus
27
What are the 3 main knee lateral rotators?
- tensor fasciae latae - bicep femoris longus - bicep femoris brevis
28
What is the function of the tensor fasciae latae?
* Can provide dynamic stabilization of the knee joint * Acts at both the hip and knee * Large hip abduction moment arm
29
What is the effect of weakness in the tensor fasciae latae?
isolated weakness may not produce disability
30
What are the effects of tightness in the tensor fasciae latae?
* Reduced ROM hip extension, adduction, lateral rotation (knee flexed) * Clinically challenging to identify (see Ober’s test) * Linked to excessive lateral deviation of the patella and anterior knee pain
31
___ strength is greater than ___ strength
extension, flexion
32
Why is extension strength greater than flexion strength?
because there is a greater mass of extensor muscles
33
What is the ideal strength ratio of the extensor muscles?
45-65%
34
What is the extension strength ratio affected by?
* Kneeposition * Mode of contraction * Speed of contraction * Sex
35
What are the 4 factors affecting knee strength?
* Age * Sex * Genetics * Joint position