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Biomechanics > Hip Biomechanics > Flashcards

Hip Biomechanics Flashcards

1
Q

ROM degrees of freedom

A

Ball & socket

6 DOF

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2
Q

Acetabular orientation

A

20 degrees anteriorly from the frontal plane

40 degrees inferiorly from the transverse plane

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3
Q

what happens to the acetabular lunate during stance phase?

articulating surface

A

the lunate surface flattens slightly as the acetabular notch widens and increases contact area and reduces peak pressure

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4
Q

non articular surface: acetabular fossa

what does it contain

A

depression deep within floor of acetabulum

contains:

  • teres ligament
  • fat synovial membrane
  • blood vessels
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5
Q

acetabular labrum

A

improves congruencey

deepens the socket and securely grips the periphery of the femoral head

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6
Q

plane of center edge angle

A

-frontal plane

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7
Q

average angle of Center edge angle

A

22-42 degrees

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8
Q

function of center edge angle

A
  • provide lateral stability
  • prevent superior dislocation
  • increases with age (why children are most prone to hip dislocation)
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9
Q

angle of inclination

A

125 degrees

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10
Q

inclination angle at birth

A

140-150 degrees

- decreases over time because of the loading across the femoral neck during walking

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11
Q

coxa varus

A

<125

hip bends inward

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12
Q

coxa valgus

A

> 125

hip bends outward

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13
Q

function of angle of torsion

A

transverse plane

  • plays a role in hip stability
  • possible cause of IR or ER
  • prevent threatening congruence during torsion
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14
Q

reason for angle of torsion

A

femoral condyles align themselves so the knee joint axis lies in frontal plane

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15
Q

trabecular intersection areas represent

A

locations of cortical bone strength

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16
Q

trabecular voids represent

A

locations of cortical bone weakness

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17
Q

hip joint capsule

A
  • joint stability

- thicker where greater stress occurs including periphery of acetabulum

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18
Q

internal capsular ligaments

A

transverse acetabular

ligamentum teres

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19
Q

transverse acetebular

A

forms tunnel for blood vessels and nerves to enter and exit hip joint

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20
Q

ligamentum teres is under tension when

A

not major stabilizer but under tension in ADD/ flexion

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21
Q

External capsular ligaments

A

illiofemoral
pubofemoral
ischiofemoral

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22
Q

illiofemoral ligament

A
  • strongest ligament at the hip
  • taut during extension
  • limits anterior displacement of femur
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23
Q

pubofemoral ligament

A

-prevents anterior displacement of femur

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24
Q

ischiofemoral

A

prevents posterior displacement of femur

tight in extension

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25
Q

majority of muscles at the hip joint are

A

unipennate biarticular , and bipennate

(1) provides good ROM with efficiency of movement
(2) provide strength

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26
Q

Hip Flexors

A
  • illiopsoas
  • rectus femoris
  • TFL
  • Sartorius
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27
Q

rectus femoris

A

most effective hip flexor when knee is flexed

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28
Q

TFL

A

Flexion, ABD, MR

29
Q

Sartorius

A
  • longest muscle in body

- flexion & ABD (depending on position of the limb)

30
Q

Hip Extensors

A

glute max

hamstrings

31
Q

glute max

A

primary used with hip in flexion (stair climbing and cycling)

32
Q

moment arm of glute max

A

shorter than other extensors –> this muscle needs to be strong to generate force

  • max force in hip in neutral
33
Q

hamstrings

A

extend hip with or without resistance

34
Q

hip abductors

A
  • gluteus medius
  • stabilize pelvis during support phase of ambulation
  • single limb support
35
Q

hip adductors

A

can produce greater isometric torque than ABD

you can create more force trying to close the legs than opening

36
Q

secondary function of hip adductors

A

flexion of hip and knee

37
Q

Hip LR

A

Quadratus femoris, piriformis, obturator & gemellus

38
Q

function of Hip Lateral Rotators

A

stabilizing role

-outward rotation of femur occurs to accommodate rotation of pelvis during every step

39
Q

Hip Medial Rotatores

A
  • no muscles have this as primary function
  • secondary: anterior glute min, TFL
  • does not require a lot of force
40
Q

Medial Rotator strength is ____ of lateral rotator strength

A

1/3

41
Q

function of hip joint

A
  1. support head, arms, trunk
  2. closed kinematic chain
  3. provide a pathway for the transmission of force between the pelvis and LE
42
Q

closed packed position of hip joint

A

full extension, medial rotation and abduction

ligaments taut

43
Q

loose-packed position

A

flexion 90 degrees, small abduction, and lateral flexion

ligaments slack

44
Q

position of greatest risk for dislocation of hip joint

A

flexed and adducted (figure 4)

mild force along the femoral axis can cause posterior dislocation

45
Q

factors affecting stability of the hip joint

A
  1. atmospheric pressure
  2. shape of the articulating surface
  3. labrum acetabular
  4. direction of the femoral neck
  5. capsule encircle the femoral neck
  6. ligaments & periarticular ms
46
Q

What is pelvic motion at the hip

A

when weight bearing all hip motions are due to pelvic motion rather than thigh motion

(situations where LR not free to move)

47
Q

Anterior Pelvic Tilt

A

ASIS rotates forward & butt rotates posteriorly

sacral angle rotates forward

occurs naturally when extra anterior mass is present

lordosis

48
Q

Posterior Pelvic Tilt

A

pubic symphysis up, ASIS back

“tuck” or “squeeze buttocks”

decrease lumbar curve

can occur at both hip joints or in single limb support

49
Q

Lateral Tilt

A

one hip joint serves as pivot and opposite iliac crest elevates (hip hiking) or drops (pelvic drop) with respect to pivot point

50
Q

stand on left leg in single support & right pelvis drops

A

left hip adduction

51
Q

Bilateral standing in sagittal plane

A

LOG falls posterior to hip joint axis (extension) checked by passive tension in the ligaments & joint capsule

52
Q

Bilateral standing in frontal plane

A

weight of head , arms and trunk = 2/3 of BW

1/3 for each hip

53
Q

symmetrical bilateral standing

A

no muscle activity needed

54
Q

asymmetrical bilateral standing

A

simulatenous contraction of the ipsilateral and contralateral ABDuctors and ADDuctors to restore balance

55
Q

unilateral standing

A

stance hip carries 5/6 of body weight

4/6 HAT + 1/4 of other LE

56
Q

importance of joint reaction forces

A

if the hip joint undergoes osteoarthritic changes leading to pain on weight bearing , the JRF must be reduced to avoid pain

57
Q

strategies to reduce joint reaction force

A
  1. weight loss
  2. reduction of abductor muscle force
  3. using the cane ipsilaterally and contralaterally
58
Q

weight loss (joint reaction force)

A

reduce 1N of body weight will reduce JRF 3N

59
Q

reduction of abductor muscle force (JRF)

A

reduce the moment arm of the gravitational force through lateral leaning of trunk towards the side of pain and weakness

60
Q

gluteus medius gait

A

if lateral trunk lean is due to hip abductor weakness

61
Q

antalgic gait

A

if lateral trunk lean is due to hip jont pain

62
Q

using the cane ipsilateral and contralateral

A

ipsi - provides benefits in energy expenditure by reducing BW by the amount of downward thrust

(lateral trunk lean is more effective)

63
Q

using the cane contralaterally

A

relieves the hip joint of 60% of its load in stance

64
Q

equation of equilibrium

A

abductor muscle torque + cane torque (latissimus dorsi) = gravitational force

65
Q

two peak forces

A

1st (4w) - just after heel strike

2nd (7w) just before toe off (abductor ms)

66
Q

Hip injury

A

subjected to 4-7 x body weight during locomotion (high repetition)

67
Q

what injury is most common in the elderly

A

femoral neck fractures

68
Q

other types of hip injury

A
  • strains to surrounding muscles

- contusions -impact force on muscles

Biomechanics (7 decks)

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