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AY BMSc Biomechanics > Unit 3: Biomechanics of the Lower Limb > Flashcards

Unit 3: Biomechanics of the Lower Limb Flashcards

1
Q

What are the 2 functions of the joints of the lower limb?

A

Movement

Weight bearing

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2
Q

What type of joint is the hip joint?

A

Ball-and-socket shaped synovial joint

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3
Q

What are the movements of the hip joint?

A

Flexion/extension
Abduction/adduction
Internal/external rottion
Circumduction

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4
Q

Describe the structure of a synovial joint

A

Covered in articular cartilage
Enclosed in a sleeve of tough fibrous tissue (joint capsule) which forms the synovial cavity.
Synovial cavity is filled with synovial fluid.
Synovial fluid is produced by the synovial membrane which lines the inner surface of the capsule

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5
Q

Why is the hip joint intrinsically stable?

A

Surrounded by a very strong articular joint capsule and several ligament. These are the surrounded by several large, strong muscles. This along with the ball-and-socket shape make the joint very stable

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6
Q

In which plane is the range of motion greatest in the ip?

A

Sagittal plane (flexion & extension)

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7
Q

What is the range of flexion of the hip?

A

140 degrees

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8
Q

What is the range of extension of the hip?

A

20 degrees

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9
Q

What is the range of abduction of the hip?

A

30 degrees

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10
Q

What is the range of adduction of the hip?

A

25 degrees

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11
Q

In which plane to internal & external rotation occur?

A

Transverse plane

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12
Q

What is the range of external rotation of the hip when it is flexed at 90 degrees?

A

90 degrees

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13
Q

What is the range of internal rotation of the hip when it is flexed at 90 degrees?

A

70 degrees

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14
Q

Why is there less internal and external rotation possible when the hip is extended?

A

Restrictions of soft tissues

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15
Q

What degree of movement is required of the hip for normal daily activities?

A

120 - flexion/extension
20 - abduction/adduction
20 - rotation

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16
Q

What is the motion in the sagittal plane of the hip when walking?

A

30 flex to 15 extension

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17
Q

Which muscles are active at the hip joint during bilateral stance?

A

Normally no muscles active

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18
Q

What percentage of body weight does the upper body (head, arms & trunk) make up?

A

70%

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19
Q

Which muscle group is used to stabilise the body in unilateral stance?

A

Abductor muscles

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20
Q

What are the 4 forces involved in calculating the hip joint force during unilateral stance?

A

Weight of lower limb
Abductor muscle force
Joint force at hip
Ground reaction force

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21
Q

Where is the insertion point of the abductor muscles?

A

Greater trochanter of the femur

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22
Q

What are the 2 articulations of the knee joint?

A

Tibiofemoral

Patellofemoral

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23
Q

What are the menisci of the knee?

A

2 crescent shaped pieces of fibrocartillage that are attached to the tibia by short tough ligaments

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24
Q

What is the purpose of menisci in the knee?

A

Make the flat top of the tibia slightly concave which aids stability. Also act as load distributors and shock absorbers

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25
Q

What is the trochlea?

A

Smooth anterior depression between the femoral condyles

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26
Q

What is the intercondylar notch?

A

Deep posterior depression between the femoral condyles that the cruciate ligaments are lodged in

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27
Q

What is the largest sesamoid bone in the body?

A

Patella

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28
Q

Where is the patella located?

A

In the tendon of the quadriceps femoris muscle

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29
Q

Does the fibula form part of the knee joint?

A

No (but does act as anchor for biceps femoris muscle and lateral collateral ligament )

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30
Q

How do the cruciate ligaments aid stability in the knee?

A

Limit forward and backward sliding of the femur on the tibia & limit hyperextension

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31
Q

How do the collateral ligaments aid knee joint stability?

A

Prevent abduction & adduction

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32
Q

How does the tibia rotate as the knee moves?

A

Knee flexes - tibia rotates internally

Knee extends - tibia rotates externally

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33
Q

Which condyle is normally bigger?

34
Q

How does the knee joint’s centre of rotation change in the sagittal plane as it flexes and extends?

A

Follows a semi circular pattern

35
Q

In which plane is the greatest range of movement in the knee?

A

Sagittal plane

36
Q

What is the range of motion in the sagittal plane of the knee?

A

few degrees of extension to about 140 degrees of flexion

37
Q

What is the range of motion in the knee in the frontal plane dependent on?

A

How much the knee is flexed

38
Q

At what degree of flexion is their maximum abduction & adduction in the knee & how many degrees?

A

Max at about 30 degrees flexion but is still only a few degrees

39
Q

What restricts rotation when the knee is in full extension?

A

Interlocking femoral & tibial condyles

40
Q

At what angle is the maximum internal and external rotation of the knee?

A

90 degrees flexion

41
Q

What is the range of internal & external rotation of the knee with it flexed at 90 degrees?

A

External - 45 degrees

Internal - 30 degrees

42
Q

What degree of movement is need in the knee for daily activities?

A

Full extension to about 115 degrees of flexion

10 degrees of rotation

43
Q

What is the most important function of the patella?

A

Increase the lever arm of the quadriceps femoris muscle (assists knee extension by displacing quadriceps tendon)

44
Q

At which point does the patella have the largest contribution to the lever arm?

A

At full extension (at flexion patella is in intercondylar notch and contributes little)

45
Q

If the patella is removed how must the knee compensate?

A

Quadriceps muscle force must increase

46
Q

Why when mensci are damaged to they have no capacity to heal?

A

As there is only a blood supply to their outer edges

47
Q

What are the 3 articulations that comprise the ankle joint?

A

Tibiotalar
Fibulotalar
Distal tibiofibular

48
Q

What are the 2 distinctive prominences on the sides of the ankle joint?

A

Medial (tibia) & lateral (fibula) malleolus

49
Q

What are the 3 most important ligaments in the ankle?

A

Anterior inferior talofibular ligament
Medial ligament
Lateral ligament

50
Q

What is the range of motion of the ankle joint?

A

10-20 dorsiflexion

25-35 plantarflexion

51
Q

What motion is needed in the ankle joint during walking?

A

10 degrees dorsiflexion

15 degrees plantarflexion

52
Q

What is a sprained ankle?

A

Partial tear of the anterior inferior talofibular ligament resulting from sudden adduction of the foot whilst the ankle is plantarflexed

53
Q

How many bones are in the foot?

54
Q

What makes up the hindfoot?

A

Talus & calcaneus (os calcis)

55
Q

What makes up the midfoot?

A

Cuboid
Medial, intermediate & lateral cuneiforms
Navicular

56
Q

What makes up the forefoot?

A

Metatarsals & phalanges

57
Q

What articulates at the subtalar joint?

A

Talus & calcaneus

58
Q

What movements does the subtalar joint allow?

A

Inversion & eversion of the foot

59
Q

What is the range of inversion & eversion at the subtalar joint?

A

Inversion - 20 degrees

Eversion - 5 degrees

60
Q

What is the walking range of motion at the subtalar joint?

61
Q

What arches make up the foot?

A

5 longitudinal arches

1 transverse arch

62
Q

What structure supports the longitudinal arch?

A

Plantar fascia

63
Q

What is the plantar fascia?

A

Heavy ligamentous structure that extends from the calcaneus to attach to the plantar aspect of the proximal phalanges

64
Q

Describe the mechanisms when bending toes

A

Plantar fascia tenses and longitudinal arches are raised thus holding the bones of the foot together

65
Q

What type of gait might someone who has broken their femur use?

A

Swing-through gait

66
Q

Why might a patient need gait analysis?

A

Improvement in CP
Determine outcome of an operation
Determine if surgery is required
Ensure alignment of protheses

67
Q

What are the phases of a gait cycle?

A 
Stance phase (R & L)
Swing phase (R & L) 
Single support (R & L) 
Double support
68
Q

When is the stance phase?

A

From heel contact to toe off

69
Q

When is the swing phase?

A

From toe off to next heel contact

70
Q

What phenomenon would be seen in a patient with weak dorsiflexor muscles?

71
Q

What is the range of motion at the hip during reciprocal gait?

A

15 ext - 30 flex

72
Q

When does peak hip extension occur in the gait cycle?

A

Just before toe off

73
Q

When is the peak amount of hip flexion in the gait cycle?

74
Q

What is the range of motion in the knee joint in reciprocal gait?

A

Few degrees of extension to 70 degrees flexion

75
Q

When is the peak amount of knee flexion in reciprocal gait?

A

During swing phase

76
Q

What is the range of motion at the ankle joint in reciprocal gait?

A

15 degrees plantarflexion - 10 degrees dorsiflexion

77
Q

What are ground reaction forces?

A

When foot is in contact with the ground it exerts an equal and opposite force

78
Q

What is the characterstic appearance of a graph of the vertical force measured using force platforms?

A

Double hump

79
Q

Why do hip extensors contract just after heel contact?

A

To prevent upper body falling forward

80
Q

Why do the hamstrings contract just after heel contact?

A

To prevent hyperextension of the knee

81
Q

Why do quadriceps contract during gait?

A

To prevent knee from bucking

82
Q

Why does the triceps surae contract just before toe off?

A

To push the foot up and off the ground

AY BMSc Biomechanics (4 decks)

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