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EDKP-206 > Lecture 9 - Biomechanics of the Knee (part 2) > Flashcards

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

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2
Q

What kind of muscle is the rectus femoris?

A

multi-joint muscle

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3
Q

What effects of weakness does the rectus femoris have?

A

reduction in hip flexion/knee extension strength

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4
Q

What kind of joint knee extensor is the vastus intermedius?

A

single joint knee extensor

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5
Q

What effect of weakness does the vastus intermedius have?

A

decreased knee ext. strength

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6
Q

What effect of tightness does the vastus intermedius have?

A

decreased knee flexion ROM

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7
Q

Which is the largest of the quad muscles?

A

vastus lateralis

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8
Q

What is the dominant knee extensor?

A

vastus lateralis

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9
Q

What is the effect of weakness in the vastus lateralis?

A

reduced knee extension strength

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10
Q

What is the effect of weakness in the vastus lateralis?

A

limits knee flexion ROM

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11
Q

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

A

10-12%

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12
Q

What does the vastus medialis balance?

A

the pull of the heads of the quads

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13
Q

What two knee extensors pull along the femur?

A

RF and VI

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14
Q

What knee extensor pulls lateral quad?

A

VL

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15
Q

Which muscle can balance with a medial pull?

A

only VM

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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
Q

What are the effects of tightness in the hamstrings?

A
  • Limits knee extension ROM (hip flexed)
  • Limit hip flexion ROM (knee extended)
26
Q

What are the 5 main knee medial rotators?

A
  • sartorius
  • gracilis
  • semitendinosus
  • semimembranosus
  • popliteus
27
Q

What are the 3 main knee lateral rotators?

A
  • tensor fasciae latae
  • bicep femoris longus
  • bicep femoris brevis
28
Q

What is the function of the tensor fasciae latae?

A
  • Can provide dynamic stabilization of the knee joint
  • Acts at both the hip and knee
  • Large hip abduction moment arm
29
Q

What is the effect of weakness in the tensor fasciae latae?

A

isolated weakness may not produce disability

30
Q

What are the effects of tightness in the tensor fasciae latae?

A
  • 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
Q

___ strength is greater than ___ strength

A

extension, flexion

32
Q

Why is extension strength greater than flexion strength?

A

because there is a greater mass of extensor muscles

33
Q

What is the ideal strength ratio of the extensor muscles?

A

45-65%

34
Q

What is the extension strength ratio affected by?

A
  • Kneeposition
  • Mode of contraction
  • Speed of contraction
  • Sex
35
Q

What are the 4 factors affecting knee strength?

A
  • Age
  • Sex
  • Genetics
  • Joint position

EDKP-206 (16 decks)

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