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Biomechanics > Exam III > Flashcards

Exam III Flashcards

1
Q

where is COM located in the human body?

A

S2

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2
Q

what is HAT?

A

(1) head, arm, trunk weight

(2) weight of the upper body acting on the LE

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3
Q

what is considered a full HAT? half HAT?

A

(1) full HAT: the full weight of the HAT on ONE LEG

half HAT: HAT distributed between TWO legs on the ground

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4
Q

what kind of force can the COM and HAT create?

A

rotation torque

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5
Q

where is the femur weakest or most susceptible to fracture? why is this area prone to fracture?

A

ward’s triangle (near mid neck); doesn’t have sufficient trabecular bone in the area

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6
Q

what is the closed pack position of the hip?

A

extension, IR, and abduction

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7
Q

what makes the closed pack position of the hip different than other joints?

A

although the ligaments of the hip are taut in closed pack, there is poor surface contact between the head and acetabulum

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8
Q

how much of the head of the hip does the acetabulum cover? what does this help provide?

A

half; provides stability

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9
Q

what is the open pack position of the hip?

A

30 degrees flexion, 30 degrees abduction, slight ER

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10
Q

which way does the femoral head project to articulate with the acetabulum?

A

anterior/medial

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11
Q

why are the muscles of the hip less likely to be impinged when compared to the shoulder?

A

the muscles attach further from the head of the hip, unlike in the shoulder where muscles attach very close to the head

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12
Q

what directions does the acetabulum face?

A

anterior, lateral, and inferior

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13
Q

what ligament of the hip doesn’t undergo much stress at all?

A

ligamentum teres; this ligament is primarily there to provide passage for blood supply for femoral head

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14
Q

what can happen with a tear of the ligamentum teres?

A

a-vascular necrosis of the head of the femur

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15
Q

what is the purpose of the transverse acetabular ligament?

A

protects vessels from being pinched

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16
Q

what are the functions of the acetabular labrum? (4)

A

(1) deepens socket (increases concavity)
(2) provides negative pressure
(3) provides proprioception and pain sensation
(4) enhance lubrication

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17
Q

what prevents superior dislocation of the hip?

A

center-edge angle

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18
Q

what complication could arise from having an increased acetabular anteversion angle?

A

more prone to anterior dislocation of the hip

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19
Q

why does the posterior side of the hip have less ligament support than the anterior side of the hip?

A

the posterior hip has a large rim of the acetabulum preventing a posterior dislocation, therefore it doesn’t need as strong ligaments to secure hip posteriorly

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20
Q

does the labrum of the hip bare weight?

A

no, it shouldn’t; not in healthy populations

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21
Q

what different mechanisms add stability to the hip joint? (4)

A

(1) ligaments and capsule
(2) muscles (provide dynamic stability)
(3) body weight compressive forces
(4) intra-articular (negative) pressure and labrum

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22
Q

what happens to the moment arm with coxa vara? what can this cause?

A

(1) the moment arm is larger

(2) increased compressive forces medially, which could increase risk for OA or stress fracture of neck

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23
Q

what happens to the moment arm with coxa valga? what can this cause?

A

(1) the moment arm is smaller

(2) weaker abductors, which increases stress superiorly

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24
Q

what is commonly associated with coxa varum?

A

(1) hip adduction
(2) genu valgum
(3) foot pronation

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25
Q

what is commonly associated with coxa valgum?

A

(1) hip abduction
(2) genu varum
(3) foot supination

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26
Q

what is the normal angle of inclination?

A

125 degrees

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27
Q

what is the angle of inclination for coxa varum?

A

105 degrees (or less)

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28
Q

what is the angle of inclination for coxa valgum?

A

140 degrees (or more)

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29
Q

excessive anteversion of the hip can lead to what compensation? why does this occur?

A

toes pointed inward; internal rotation of the hip improves joint congruity

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30
Q

how much hip anteversion does an infant usually have?

A

40 degrees

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31
Q

what is considered “normal” hip anteversion by the age of about 16?

A

15 degrees

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32
Q

excessive anteversion of the hip that persists into adulthood can lead to what problems?

A

(1) increased risk of hip dislocation
(2) articular incongruence
(3) increased joint contact stress
(4) increased wear on cartilage or labrum

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33
Q

what are the two main ligaments of the anterior hip? which is the strongest of the hip?

A

(1) iliofemoral ligament (strongest)

(2) pubofemoral

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34
Q

what ligament runs posterior to the hip?

A

(1) ischiofemoral

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35
Q

which motion makes all 3 hip ligaments taut?

A

full hip extension (think closed pack)

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36
Q

which ligaments of the hip are the strongest?

A

anterior ligaments (iliofemoral & pubofemoral)

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37
Q

what structures become taught at end-range hip flexion with knee EXTENDED (1)

A

(1) hamstrings

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38
Q

what structures become taught at end-range hip flexion with knee FLEXED? (2)

A

(1) posterior/inferior capsule

(2) glute max

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39
Q

what structures become taught at end-range hip extension with knee EXTENDED? (5)

A 
PRIMARY
(1) iliofemoral ligament
(2) anterior capsule
SECONDARY
(3) pubofemoral ligament
(4) ischiofemoral ligament
(5) iliopsoas
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40
Q

what structures become taught at end-range hip extension with knee FLEXED? (1)

A

(1) rectus femoris

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41
Q

what structures become taught at end-range hip abduction? (2)

A

(1) pubofemoral ligament

(2) adductors

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42
Q

what structures become taught at end-range hip adduction? (2)

A

(1) IT band

2) abductors (TFL, glute med

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43
Q

what structures become taught at end-range IR? (2)

A

(1) ischiofemoral ligament

2) external rotators (piriformis, glute max

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44
Q

what structures become taught at end-range hip ER? (3)

A

(1) iliofemoral ligament
(2) pubofemoral ligament
(3) internal rotators (TFL, glute minimus)

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45
Q

what is a normal center edge angle?

A

35 degrees

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46
Q

what is the most vulnerable position for the hip to be in for a dislocation to occur? why?

A

flexion, adduction, slight IR; ligaments are relaxed and trauma can cause posterior dislocation

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47
Q

what is considered excessive anteversion of the hip?

A

35+ degrees

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48
Q

in an OPEN CHAIN, what motions occur when the hip is flexed?

A

(1) posterior pelvic tilt

(2) flexion of the lumbar spine

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49
Q

in an OPEN CHAIN, what motions occur when the hip is extended?

A

(1) anterior pelvic tilt

(2) extension of the lumbar spine

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50
Q

in an OPEN CHAIN, what motions occur when the hip is abducted?

A

(1) ipsilateral side flexion of lumbar spine

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51
Q

in an OPEN CHAIN, what motions occur when the hip is adducted?

A

(1) contralateral side flexion of lumbar spine

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52
Q

in an OPEN CHAIN, what motions occur when the hip is internally rotated?

A

(1) inflare of the pelvis

(2) contralateral rotation of the lumbar spine

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53
Q

in an OPEN CHAIN, what motions occur when the hip is externally rotated?

A

(1) outflare of the pelvis

(2) ipsilateral rotation of the lumbar spine

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54
Q

what is an ipsidirectional lumbopelvic rhythm?

A

when the lumbar spine and pelvis rotate in the same direction (ex. when bending over to pick up a box)

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55
Q

what is a contradirectional lumbopelvic rhythm?

A

when the lumbar spine and pelvis rotate in opposite directions

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56
Q

what are two causes of a contradirectional lumbopelvic rhythm?

A

(1) anterior pelvic tilt

(2) posterior pelvic tilt

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57
Q

when you have an anterior pelvic tilt, what happens at the lumbar spine?

A

the spine extends to compensate for the anterior tilt

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58
Q

when you have a posterior pelvic tilt, what happens at the lumbar spine?

A

the spine flexes to compensate for the posterior tilt

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59
Q

when the hip flexes in an open kinematic chain, which way does the pelvis rotate?

A

posteriorly

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60
Q

how is hip flexion accomplished in a closed kinematic chain?

A

by the pelvis tilting anteriorly

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61
Q

how is hip extension accomplished in a closed kinematic chain?

A

by the pelvis tilting posteriorly

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62
Q

how is the hip abducted in a closed kinematic chain?

A

by hiking the iliac crest on the contralateral (non-support) side

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63
Q

how is the hip adducted in a closed kinematic chain?

A

by lowering the iliac crest on the contralateral (non-support) side

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64
Q

when in the gait cycle does the hip adduct? when does it abduct?

A

(1) adducts: 20-30%

(2) abducts: 60%

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65
Q

in a closed kinetic chain, what happens when the hip is internally rotated?

A

contralateral forward rotation of the pelvis

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66
Q

in a closed kinetic chain, what happens when the hip is externally rotated?

A

contralateral backwards rotation of the pelvis

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67
Q

when the hip is flexed, which direction is the glide of the femoral head?

A

posterior glide

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68
Q

when the hip is extended, which direction is the glide of the femoral head?

A

anterior glide

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69
Q

when the hip is abducted, which direction is the glide of the femoral head?

A

inferior glide

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70
Q

when the hip is internally rotated, which direction is the glide of the femoral head?

A

posterior glide

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71
Q

when the hip is externally rotated, which direction is the glide of the femoral head?

A

anterior glide

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72
Q

what muscles assist with performing an anterior pelvic tilt?

A

(1) force-couple between hip flexors and low back extensors

(2) iliopsoas, sartorious, erector spinae

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73
Q

weakness of what muscles can lead to an increased anterior pelvic tilt? why does this occur?

A

(1) weak abdominals; the hip flexors have a strong inferior pull on the pelvis, and the abs stabilize the pelvis by pulling the pelvis superiorly
(2) when the abs are weak, the hip flexors over power the abdominals and pull the pelvis anteriorly

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74
Q

how does an increased anterior pelvic tilt affect the spine?

A

increased lumbar lordosis

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75
Q

how does a hip flexor contracture cause metabolically inefficiency?

A

the extensors are expend more energy to prevent further hip flexion

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76
Q

what can hip flexor contractures lead to? (3)

A

(1) increased lumbar lordosis
(2) spine pain
(3) knee OA

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77
Q

what muscles assist with performing an posterior pelvic tilt?

A

(1) force-couple between hip extensors and low back flexors (core muscles)
(2) glute max, hamstrings, external obliques, rectus abdominis

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78
Q

when going from a completely erect standing position to bent over, what muscles are initially more active? what muscles become more active the more you flex the hips?

A

(1) initially, the glutes are more active

(2) the more the hip is flexed, glute activation decreases and hamstring and adductor activation increases

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79
Q

what muscles are required for stabilization of the spine when climbing uphill?

A

low back extensors (the multifidi)

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80
Q

during a single leg stance, how much force is required of the abductors to stabilize the pelvis?

A

twice the body weight

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81
Q

what happens when the abductors are weak and can’t provide the the required stability to the pelvis?

A

the pelvis drops on the contralateral side during gait (trendelenburg gait)

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82
Q

at what angle are the hip abductors the strongest? what angle are they the weakest?

A

(1) strongest near 0 degrees abduction (neutral)

(2) weakest near 40 degrees abduction

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83
Q

adduction usually occurs in combination of movement in other planes; which plane?

A

sagittal; adduction usually occurs with flexion or extension

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84
Q

when the hip is adducted, what muscle helps to eccentrically control the velocity and drop of the adducting hip?

A

glute medius

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85
Q

how does the adductor longus act as both a hip flexor and hip extensor?

A

(1) when the hip is extended, the adductor longus acts as a hip flexor
(2) when the hip is flexed, the adductor longus acts as a hip extensor

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86
Q

when does the piriformis act as an internal rotator?

A

when the hip is flexed to 90 degrees

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87
Q

when does the glute med act as an external rotator?

A

near neutral (0 degrees)

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88
Q

when is the glute med strongest as an internal rotator?

A

near 90 degrees of hip flexion

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89
Q

what group of muscles can act secondarily as internal rotators?

A

the adductors (specifically, the adductor longus)

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90
Q

when are the internal rotators most active during gait?

A

the first 30% of the gait cycle

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91
Q

during what athletic manuever are the external rotators very active? how does this occur?

A

cutting motions; with one leg planted, the external rotators contract causing the contralateral pelvis to move posteriorly

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92
Q

what muscles assist the external rotators with external rotation of the hip? (think closed chain)

A

back extensor muscles

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93
Q

what are the strongest muscles of the hip? what are the weakest?

A

(1) extensors (strongest)
(2) flexors
(3) adductors
(4) abductors
(5) internal rotators
(6) external rotators (weakest)

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94
Q

why is the cane placed on the unaffected side when ambulating? (2)

A

(1) moves the COP and LOG away from the injured side
(2) the lever arm is 4x longer; the UE muscles are in a much better advantage to produce force (triceps and shoulder extensors)

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95
Q

when does developmental hip dysplasia typically manisfest?

A

at birth or within the first few years of life

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96
Q

what are the causes of developmental hip dysplasia? (3)

A

(1) joint laxity
(2) abnormal intra-uterine positioning
(3) post natal positioning

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97
Q

what is Legg-Calve-Perthes disease? what age does this usually occur?

A

(1) avascular necrosis of the femoral head

(2) children aged 4-10 years

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98
Q

during what activity do the adductors act as hip flexors and extensors? what activity do the adductors act as internal rotators?

A

(1) flexors and extensors during running

(2) internal rotators during walking

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99
Q

what is a normal femoral-tibial angle?

A

170-175 degrees

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100
Q

what is the femoral-tibial angle with genu valgum and genu varum?

A

(1) genu valgum: <= 165 degrees

(2) genu varum: >= 180 degrees

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101
Q

how are forces redistributed at the knee with genu valgum?

A

(1) medial structures under tension

(2) lateral structures shorten and lateral condyles are compressed

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102
Q

how are forces redistributed at the knee with genu varum?

A

(1) lateral structures under tension

(2) medial structures shorten and medial condyles are compressed

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103
Q

where can injury occur due to genu valgum? what about genu varum?

A

genu valgum
(1) medial knee pain: ligaments and capsule
(2) lateral knee pain: meniscus and cartilage
genu varum
(1) medial knee pain: meniscus and cartilage
(2) lateral knee pain: ligaments and capsule

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104
Q

what condition at the knee makes a person more prone to ACL and MCL tears?

A

genu valgum

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105
Q

what condition at the knee makes a person more prone to medial condyle OA?

A

genu varum

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106
Q

what condition at the knee makes a person more prone to PF syndrome, subluxation, and lateral dislocations of the patella?

A

genu valgum

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107
Q

what are two deformities associated with genu varum?

A

(1) osteitis deformans

(2) osteomalacia

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108
Q

what patient populations may be associated with genu valgum?

A

(1) obese patients

(2) patients with weak quads and hip abductors

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109
Q

what is considered a normal Q angle?

A

10-15 degrees

110
Q

what is considered an abnormal Q angle?

A

> 20 degrees

111
Q

how does a larger Q angle affect forces at the knee?

A

increases the forces that pull the patella laterally

112
Q

what are some different factors that increase the Q angle? (7)

A

(1) genu valgus
(2) femoral anteversion
(3) external tibial torsion
(4) lateral displacement of tibial tuberosity
(5) weak VMO
(6) foot overpronation
(7) tight lateral retinaculum

113
Q

what is the Insall-Salvati ratio?

A

ratio of patellar tendon length to length of the patella

114
Q

what is patella alta? what is it associated with?

A

(1) high patella

(2) excessive lateral tracking of the patella making it more prone to subluxation; PF syndrome

115
Q

what is patella baja? what is the most common cause of this condition?

A

(1) low patella

(2) rare side effect of surgery; can limit ROM and cause pain

116
Q

where is the synovial fluid of the knee forced during full extension?

A

anteriorly

117
Q

where is the synovial fluid of the knee forced during full flexion?

A

posteriorly

118
Q

what position is the capsule under the least tension and most comfortable when joint effusion is present?

A

a semi-flexed position

119
Q

what passive (2) and active (1) structures reinforce the capsule of the knee anteriorly?

A

PASSIVE
(1) patellar tendon and patellar retinacular fibers
ACTIVE
(1) quads

120
Q

what passive (3) and active (3) structures reinforce the capsule of the knee laterally?

A 
PASSIVE
(1) LCL
(2) lateral patellar retinaculum
(3) IT band
ACTIVE
(1) biceps femoris, popliteal tendon, lateral head of gastroc
121
Q

what passive (2) and active (3) structures reinforce the capsule of the knee posteriorly?

A 
PASSIVE
(1) oblique popliteal ligament
(2) arcuate popliteal ligament
ACTIVE
(1) popliteus, gastroc, hamstrings
122
Q

what passive (3) and active (1) structures reinforce the capsule of the knee posterior-laterally?

A 
PASSIVE
(1) arcuate popliteal ligament
(2) LCL
(3) popliteofibular ligament
ACTIVE
(1) tendon of popliteus
123
Q

what passive (3) and active (3) structures reinforce the capsule of the knee medially?

A 
PASSIVE
(1) MCL
(2) medial patellar retinaculum
(3) posterior oblique ligament
ACTIVE
(1) tendons of the medial hamstrings, sartorious, gracilis
124
Q

the knee has how many bursae?

A

14

125
Q

which meniscus of the knee is larger?

A

medial meniscus

126
Q

what are some of the functions of the menisci? (6)

A

(1) increase concavity of tibial condyle (stability)
(2) weight distribution
(3) reduce friction
(4) lubricates articular cartilage
(5) provides proprioception
(6) helps absorb shock (muscles are main shock absorbers)

127
Q

what muscle attaches to the medial meniscus? what attaches to the lateral meniscus?

A

(1) medial: semimembranosus

(2) lateral: popliteus

128
Q

when the meniscus is injured and stress distribution becomes abnormal, what can this cause?

A

increased risk of OA

129
Q

what is considered normal ROM at the knee joint for flexion and extension?

A

(1) flexion: 140 degrees

(2) extension: 0 - 10 degrees hyperextension are WNL

130
Q

what is genu recurvatum?

A

hyperextension of the knee >10 degrees

131
Q

how much tibial rotation occurs at the knee when it’s fully extended?

A

0 degrees; the knee is locked

132
Q

at what degree of knee flexion is tibial rotation the greatest? how much tibial rotation occurs?

A

(1) 90 degrees of knee flexion

(2) 40-45 degrees of total rotation

133
Q

what is the ratio of ER to IR at the knee?

A

2:1 (twice as much ER than IR)

134
Q

how much total abduction and adduction occurs at the knee?

A

6 degrees (passively)

135
Q

in an open chain, which direction does the rotation of the knee occur?

A

SAME DIRECTION

femur is stationary and the rotation occurs in the same direction of the tibia

136
Q

in a closed chain, which direction does the rotation of the knee occur?

A

OPPOSITE DIRECTIONS
the tibia is fixed, and the femur is moving on the tibia
(1) ER of the knee occurs with IR of the femur
(1) IR of the knee occurs with ER of the femur

137
Q

how much extension at the knee is required for normal gait, stair climbing, and running?

A

0 degrees (full extension)

138
Q

how much knee flexion is required for normal gait?

A

60 degrees

139
Q

how much knee flexion is required for stair climbing?

A

80 degrees

140
Q

how much knee flexion is required for sitting and rising from most chairs?

A

90 degrees

141
Q

how much knee flexion is required for sitting and rising from a toilet seat?

A

115 degrees

142
Q

how much knee flexion is required for “advanced function?”

A

> 115 degrees

143
Q

which way does the tibia glide with knee extension in an OPEN CHAIN?

A

(1) concave tibia moving on convex femur; SAME DIRECTION

(2) anterior glide

144
Q

which way does the tibia glide with knee flexion in an OPEN CHAIN?

A

(1) concave tibia moving on convex femur; SAME DIRECTION

(2) posterior glide

145
Q

which way does the femur glide with knee extension in a CLOSED CHAIN?

A

(1) convex femur moving on concave tibia; OPPOSITE DIRECTION

(2) posterior glide

146
Q

which way does the femur glide with knee flexion in a CLOSED CHAIN?

A

(1) convex femur moving on concave tibia; OPPOSITE DIRECTION

(2) anterior glide

147
Q

how does the screw home mechanism occur in an OPEN CHAIN?

A

when the knee extends, the tibia externally rotates

148
Q

how does the screw home mechanism occur in a CLOSED CHAIN?

A

when the knee extends, the femur internally rotates

149
Q

what factors guide the screw home mechanism? (3)

A

(1) shape of medial femoral condyle
(2) tension in ACL
(3) lateral pull of quads

150
Q

how does the popliteus “unlock” the knee in regards to the screw home mechanism? (open chain and closed chain)

A

OPEN CHAIN
(1) when the popliteus contracts, it internally rotates the tibia during knee flexion
CLOSED CHAIN
(1) when the popliteus contracts, it externally rotates the femur during knee flexion

151
Q

what motion does the MCL restrict? (3)

A

(1) valgus
(2) extension
(3) ER of the knee

152
Q

does the MCL prevent valgus more when the knee is flexed or extended?

A

during knee flexion

78% restraint during flexion vs. 57% during extension

153
Q

what motion does the LCL restrict? (3)

A

(1) varus
(2) extension
(3) rotational forces of tibia

154
Q

does the LCL prevent varus more when the knee is flexed or extended?

A

during knee flexion

69% restraint during flexion vs. 55% during extension

155
Q

what motions does the ACL restrict? (3)

A

(1) anterior translation of the tibia (posterior glide of femur)
(2) varus AND valgus
(3) rotational forces of tibia (IR and ER)

156
Q

what motions does the ACL restrict?

A

(1) posterior translation of the tibia (anterior glide of femur)
(2) varus AND valgus
(3) rotational forces of tibia (IR and ER)

157
Q

what position are the ligaments of the knee most taut?

A

full extension

158
Q

what structure does the IT band protect during knee flexion? how is this accomplished?

A

(1) protects the PCL

(2) IT band slides posterior to the condyles, controlling anterior translation of the femur

159
Q

what structure does the IT band protect during knee extension? how is this accomplished?

A

(1) protects the ACL

(2) IT band slides anterior to the condyles, controlling posterior translation of the femur

160
Q

what are the most commonly injured knee ligaments? (2)

A

ACL and MCL

161
Q

at what angle of knee flexion is contact between the patella and femur greatest? what does this mean?

A

90 degrees; patella in the best position to resist stress at 90 degrees

162
Q

what part of the patella is in contact with the femur at 20, 90, and 135 degrees of knee flexion?

A

(1) 20 degrees: inferior pole (not stable)
(2) 90 degrees: medial and lateral patellar facets (most stable)
(3) 135 degrees: odd facet and edge of lateral facet (not stable)

163
Q

as the external force on the PF joint increases, what happens to the contact area and why?

A

(1) the contact area increases to disperse large compression forces
(2) this occurs up to 90 degrees of flexion and then beyond 90 degrees the contact area decreases again

164
Q

what position is the torque on the patellofemoral joint the largest?

A

full extension in an open kinematic chain (ex. leg extension machine)

165
Q

what position is STRESS on the patellofemoral joint the highest?

A

despite having the best contact, 90 degrees of knee flexion in a CKC puts the most stress on the PF joint (the knee is also in best position to be stressed)

166
Q

what causes abnormal tracking of the patella often seen in PFS? (7)

A 
FUNCTIONAL
(1) IT band adhering to VL
(2) tight quads (VMO specifically)
(3) weak hip abductors and ERs
STRUCTURAL
(1) genu valgus/varus
(2) femoral ante/retroversion
(3) external tibial torsion
(4) pronated foot
167
Q

in what position does the tibiofemoral joint have the greatest surface contact and is in the best position to resist stress?

A

full knee extension (0 degrees)

168
Q

what movement might hurt patients with OA of the tibiofemoral joint?

A

squatting (smaller surface area as the knee flexes)

169
Q

which muscle group at the knee is stronger, knee flexors or extensors? how much stronger?

A

knee extensors; 2-3x stronger

170
Q

what is the function of the quads during isometric, eccentric, and concentric muscle contractions?

A

(1) isometric: stabilizes the knee
(2) eccentric: shock absorption
(3) concentric: knee extension (ex. stand from sitting)

171
Q

in an OPEN chain, when is the external torque imposed on the quadriceps highest?

A

full extension (0 degrees) (think leg extension)

172
Q

in a CLOSED chain, when is the external torque imposed on the quadriceps highest?

A

90 degrees of knee flexion; (think the bottom of a squat)

173
Q

when are the quads strongest? when are they weakest?

A

(1) strongest: mid range (45 degrees)

2) weakest: full extension (0 degrees

174
Q

what are two main functions of the knee flexors during gait?

A

(1) eccentrically decelerate the leg during the terminal swing phase
(2) flex the knee during swing phase so the toes don’t hit the ground and you trip

175
Q

how does the short head of the biceps femoris and the pes anserinus muscle group control knee rotation in a closed kinematic chain?

A

(1) biceps femoris: accelerates femur internally (the knee joint moves into ER)
(2) pes anserinus: decelerate and limit ER at the knee
(these muscle groups work to accelerate and decelerate rotation at the knee)

176
Q

when are the knee flexors strongest? when are they weakest?

A

(1) strongest: near full extension (20 degrees of flexion)

(2) weakest: 90 degrees of flexion

177
Q

how do the knee flexors and extensors work synergistically during running?

A

(1) quads contract to maintain the knee extended

2) with the knee extended, the hamstrings contract and cause hip extension (assist the glutes

178
Q

when the hip is flexed and knee is extended simultaneously, what occurs to the quads and hamstring muscles?

A

(1) active insufficiency of the quads
(2) passive insufficiency of the hamstrings
(efficiency is decreased)

179
Q

when the hip is extended and knee is flexed simultaneously, what occurs to the quads and hamstring muscles?

A

(1) active insufficiency of the hamstrings
(2) passive insufficiency of the quads
(efficiency is decreased)

180
Q

what percentage of ACL sport related injuries are non-contact? what position of the leg is the ACL most commonly injured?

A

(1) 70%

(2) knee flexed with foot planted on the ground

181
Q

what are 3 factors associated with non-contact ACL injuries?

A

(1) strong quad activation over a flexed or nearly extended knee
(2) valgus collapse of the
knee
(3) excessive
external rotation of the
knee (excessive IR of the femur or ER of the tibia)

182
Q

are closed chain or open chain exercises better for the ACL when rehabbing? why?

A

closed chain; the tensile forces placed through the ACL are less when the hamstrings co-contract with the quads (closed chain) compared to the quads contracting alone (open chain)

183
Q

what is an important factor in ACL injury prevention?

A

motor education; teaching athletes to land properly (among other movements) reduces the strain placed on the ACL

184
Q

after recovery from an ACL injury, when can walking, jogging, and sports be resumed?

A

weeks 3-6: walking
weeks 7-12: jogging / strength training
months 4-7: sagittal plane sports
>8 months: slow introduction to cutting sports

185
Q

what motions tend to worsen pain in patients with PFS? (3) what is one possible cause of PFS?

A

(1) squatting
(2) stair ascension
(3) sitting with knees flexed for extended periods of time
Possible Cause
-stress intolerance of articular cartilage

186
Q

what is the relationship between Q angle and PFS?

A

increased Q angle contributes to PFS

187
Q

where may OA occur in patients with genu varum?

A

medial side of the knee

188
Q

what is the most common cause of genu recurvatum? how is this condition usually managed?

A

(1) weak quads (poliomyelitis and spinal cord injury also causes)
(2) brace or heel insole

189
Q

what is involved with the PT management of PFS? (4)

A

(1) strengthen hip abductors and ERs
(2) strengthen VMO
(3) insole to improve foot pronation
(4) taping and bracing to guide tracking

190
Q

what bones make up the hind foot, midfoot, and forefoot?

A

(1) hind foot: talus and calcaneus
(2) navicular, cuboid, 3 cuneifrom
(3) forefoot: metatarsals and phalanges

191
Q

how does the ankle function to provide stability? (2) how does it provide mobility? (2)

A

Stability
(1) provide BOS with minimal energy expenditure
(2) act as rigid lever for push-off during gait
Mobility
(1) dampens torsional forces
(2) absorbs shock and allow foot to conform to uneven terrain

192
Q

what are the triplanar movements that make up pronation?

A

(1) dorsiflexion
(2) eversion
(3) abduction

193
Q

what are the triplanar movements that make up supination?

A

(1) plantarflexion
(2) inversion
(3) adduction

194
Q

what direction is valgus at the ankle?

A

eversion

195
Q

what direction is varus at the ankle?

A

inversion

196
Q

what is the concave / convex rule at the PROXIMAL tibiofibular joint?

A

concave fibular head facet moving on a convex tibial facet

197
Q

what is the concave / convex rule at the DISTAL tibiofibular joint?

A

convex fibular facet moving on a concave tibial facet

198
Q

what type of joint is the distal tibiofibular joint?

A

syndesmosis joint (no synovial cavity)

199
Q

are the ligaments at the distal tibiofibular joint weak or strong? what ligaments passive structures support this joint?

A

very strong

(1) anterior tibiofibular ligament
(2) posterior tibiofibular ligament
(3) interosseous membrane

200
Q

what accessory motion occurs at the proximal tibiofibular joint?

A

superior fibular glide with dorsiflexion (crural) and pronation (subtalar)

201
Q

what accessory motion occurs at the distal tibiofibular joint?

A

gapping between the distal tibia and fibula with dorsiflexion

202
Q

how many planes of motion does the talocrural joint move in? what is the main degree of freedom the talocrural joint is responsible for?

A

(1) 3 (triplanar joint)

(2) sagittal plane: dorsiflexion / plantarflexion

203
Q

when is the congruency (stability) of the talus greatest? why?

A

(1) dorsiflexion

(2) talus fits into ankle mortise

204
Q

what accessory movement occurs at the talocrural joint with dorsiflexion in an OPEN CHAIN?

A

(1) CONVEX talus moving on CONCAVE tibia

(2) posterior glide

205
Q

what accessory movement occurs at the talocrural joint with plantarflexion in OPEN CHAIN?

A

(1) CONVEX talus moving on CONCAVE tibia

(2) anterior glide

206
Q

what active and passive structures limit dorsiflexion? (3)

A 
Knee Extended
(1) triceps surae
Knee Flexed
(1) soleus
(2) posterior capsule and ligaments
207
Q

what active and passive structures limit plantarflexion? (2)

A

(1) dorsiflexors

(2) anterior capsule and ligaments

208
Q

what structural and functional problems may limit dorsiflexion?

A

(1) osteophytes on the dorsal talus or anterior distal tibia

(2) tight intrinsic muscles of foot or tight plantar fascia

209
Q

what side of the ankle has stronger passive structures? which has weaker?

A

(1) lateral side of the ankle has weaker ligaments

(2) medial side has stronger ligaments

210
Q

what are the most commonly injured ligaments of the ankle?

A

(1) ATFL (most commonly injured)
(2) calcaneofibular (2nd most most commonly injured)
(3) PTFL

211
Q

what are the two main functions of the retinacula of the foot and ankle?

A

(1) pulley system for muscles

(2) proprioception for joint protection

212
Q

what motion is the subtalar joint primarily responsible for providing?

A

pronation and supination (triplanar motion occurs at this joint)

213
Q

what direction are the roll and glide with pronation and supination of the subtalar joint in an OPEN chain?

A

talus and calcaneus move in the SAME direction with pronation and supination

214
Q

what direction are the roll and glide with pronation and supination of the subtalar joint in a CLOSED chain?

A

OPPOSITE directions

(1) pronation: talus moves medially, while calcaneus glides laterally
(2) supination: talus moves laterally, while calcaneus glides medially

215
Q

internal rotation of a weight bearing leg causes what at the subtalar joint?

A

pronation (pronation at subtalar joint also causes IR of the leg)

216
Q

external rotation of a weight bearing leg causes what at the subtalar joint?

A

supination (supination at subtalar joint also causes ER of the leg)

217
Q

in a closed chain, where does frontal and transverse plane movement come from at the subtalar joint?

A

(1) frontal: movement of calcaneus

(2) transverse: movement of talus

218
Q

what motions occur with pronation in a CLOSED chain? (4)

A

(1) eversion of the calcaneus
(2) plantarflexion of the talus
(3) adduction of the talus
(4) IR of the leg

219
Q

going up the kinetic chain, what does over pronation cause?

A

(1) internal rotation of the leg (and adduction at the knee)
(2) causing an anterior pelvic tilt
(3) causing extension of the ipsilateral lumbar spine

220
Q

what motions occur with supination in a CLOSED chain? (4)

A

(1) inversion of the calcaneus
(2) dorsiflexion of the talus
(3) abduction of the talus
(4) ER of the leg

221
Q

what motions occur with pronation in an OPEN chain? (5)

A

(1) eversion of the calcaneus
(2) dorsiflexion of the calcaneus
(3) abduction of the calcaneus
(4) abduction of the talus
(5) dorsiflexion of the talus

222
Q

what motions occur with supination in an OPEN chain? (5)

A

(1) inversion of the calcaneus
(2) plantarflexion of the calcaneus
(3) adduction of the calcaneus
(4) adduction of the talus
(5) plantarflexion of the talus

223
Q

what two joints make up the midtarsal joint?

A

(1) talonavicular

(2) calcaneocuboid

224
Q

which joint of the two midtarsal joint allows more motion?

A

talonavicular joint

225
Q

what causes cuboid syndrome? what are symptoms of this syndrome?

A

(1) forceful eversion of the cuboid while the calcaneus is inverted
(2) pain during push-off of gait

226
Q

what ligaments protect the talonavicular joint? (4)

A

(1) inferior: spring ligament
(2) medial: deltoid
(3) superior: bifurcate ligament
(4) superior: talonavicular ligament

227
Q

which bone is concave and which bone is convex at the talonavicular joint?

A

(1) convex: talus

(2) concave: navicular

228
Q

what are the 2 main functions of the midtarsal joint?

A

(1) add to the ROM at the subtalar joint (OKC)

2) compensate the forefoot for hindfoot positioning in a CKC (pronate or supinate

229
Q

when pronation occurs at the subtalar joint, how can the midtarsal joint compensate?

A

it can either pronate OR supinate

230
Q

when supination occurs at the subtalar joint, how can the midtarsal joint compensate?

A

supination, NOT pronation (limited ability for midtarsal joint to pronate when subtalar joint supinates)

231
Q

what is a Lisfranc injury?

A

(1) fracture to base of the 2nd metatarsal

(2) ligament between 1st cuniform and 2nd metatarsal

232
Q

what ligament provides stability and prevents excessive splaying of the metatarsal heads?

A

deep transverse metatarsal ligament

233
Q

which rays of the foot does triplanar motion occur?

A

1st and 5th (more motion on the medial and lateral sides of the foot)

234
Q

which ray of the foot has the least amount of motion?

A

2nd

235
Q

what are some main functions of the tarsometatarsal joint?

A

(1) hollow and flatten the foot
(2) augments midtarsal joint function
(3) provides pronation and supination when hindfoot and midfoot are at end range

236
Q

how do you lock the foot?

A

with the toes in full extension

237
Q

when the foot is locked (toes fully extended), all ankle joints are locked except which one?

A

the talocrural joint

238
Q

with extreme subtalar pronation, what occurs at the forefoot?

A

supination at the forefoot

239
Q

with extreme subtalar supination, what occurs at the forefoot?

A

pronation at the forefoot

240
Q

what is a high longitudinal foot arch associated with?

A

supination

241
Q

what is a low longitudinal foot arch associated with?

A

pronation

242
Q

what is the concave/convex rule at metatarsophalangeal joint in an OPEN chain?

A

concave phalange moving on a convex metatarsal (roll and glide the same)

243
Q

what is the concave/convex rule at metatarsophalangeal joint in a CLOSED chain?

A

convex metatarsal moving on a concave phalange

roll and glide opposite

244
Q

what are 2 functions of the two sesamoid bones on the bottom of the 1st metatrasophalange?

A

(1) serve as pulley for the flexor hallucis brevis

(2) protect the tendons of the flexor hallucis longus

245
Q

what is turf toe and how is it caused?

A

(1) sprain of the ligaments of the big toe

(2) caused by forced hyperextension of the big toe

246
Q

what is the keystone of the longitudinal arches of the foot?

A

talus

247
Q

what is the keystone of the transverse arch of the foot?

A

intermediate cuneiform

248
Q

when do the arches of the foot start to develop?

A

when a child starts weight bearing (walking)

249
Q

what are 3 structures that provide passive support to the arches of the feet? (3)

A

(1) spring ligament
(2) interosseous talocalcaneal ligament
(3) plantar aponeurosis

250
Q

what are the two main functions of the arches of the foot? how are these functions accomplished?

A

(1) mobility
(a) dampen impact forces
(b) dampen rotational forces
(c) adapt to changes of ground surfaces
(2) stability
(a) distribute weight through the foot
(b) convert flexible foot to rigid level during gait

251
Q

what motion causes the plantar aponeurosis to tighten?

A

MTP extension

252
Q

what percentage of the weight of the body passes through the talus in standing?

A

(1) 50% through each each talus in bilateral standing

(2) 100% in unilateral standing

253
Q

how is weight distributed through the joints of the foot in standing?

A

(1) 50% of the weight falls posterior to subtalar joint to calcaneus
(2) 50% falls anterior through the talonavicular and calcaneocuboid joints

254
Q

what structure helps with shock absorption at the heel during gait and running?

A

heel fat pad

255
Q

why does wearing open heel shoes reduce the ability of the heel pad to absorb shock?

A

open heel shoes allow the fat pad to spread out more to the sides of the heel

256
Q

what can said be about the intrinsic muscle support of the arches of the foot during walking and running?

A

intrinsic foot muscles aren’t very active during walking or standing; they’re much more active during running

257
Q

what muscles support the medial arch of the foot? (3)

A

(1) tibialis posterior
(2) flexor digitorum longus
(3) flexor hallucis longus

258
Q

what muscles support the lateral and transverse arches of the foot? (1)

A

(1) peroneus longus

259
Q

muscles passing medial to the subtalar joint cause what motion at the ankle? what about muscles passing lateral to the subtalar joint?

A

(1) medial: supination

(2) lateral: pronation

260
Q

what muscles of the ankle control pronation at the foot?

A

supinators (tibialis posterior); medial muscles eccentrically control pronation

261
Q

what are the strongest muscles of the foot and ankle? which are the weakest?

A

(1) plantarflexors (strongest)
(2) dorsiflexors
(3) supinators
(4) pronators (weakest)

262
Q

how does the triceps surae help lock the foot into a rigid lever?

A

the Achilles tendon passes medial to the subtalar joint, supinating the foot and locking it during weight bearing activities

263
Q

what percentage of plantarflexion is the triceps surae responsible for?

A

95%

264
Q

what muscles are important for balance and eccentrically controlling MTP extension? (2)

A

(1) flexor hallucis longus

(2) flexor digitorum longus

265
Q

what arches does the peroneus longus tendon support?

A

(1) lateral arch

(2) transverse arch

266
Q

what is the key supinator of the foot?

A

anterior tibialis

267
Q

what type of lever is the gastroc?

A

type 2 (resistance in the middle)

268
Q

what muscles stabilize the MTP joints and extend the IP joints?

A

(1) lumbricals
(2) dorsal interossei
(3) plantar interossei

269
Q

what is pes cavus? how is the shock absorption with pes cavus?

A

(1) foot is more supinated (subtalar and transverse tarsal joints)
(2) poor shock absorption; foot is locked and inflexible

270
Q

what is pes planus? how is the shock absorption with pes cavus?

A

(1) foot is more pronated (subtalar and transverse tarsal joints)
(2) better shock absorption than pes cavus; foot is overly mobile

271
Q

can insoles help correct pes cavus or pes planus?

A

pes planus; it does so by increasing supination of the foot

272
Q

generally speaking, what structures are the main stabilizers of the arches of the foot?

A

passive structures (bones and ligaments); muscles play a smaller role

Biomechanics (4 decks)

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