Biomechnics unit 3 Biomech of the lower limb - deck 1

Question 1

Is walking demanding on the human body?

Answer 1

Yes - it is one of the most commonly executed human activities and is also one of the most demanding.

Question 2

What must orthopaedic and rehabilitation devices, such as joint replacements, fracture fixation devices and lower limb prostheses and orthoses, be able to withstand the demands of ?

Answer 2

The demands placed on them when walking

Question 3

When designing an Orthopaedic and rehabilitation device what are the main demands on the device that must be considered to ensure the patient gets as much function as possible and so that the device does not break during usage ?

Answer 3

1. The range of joint motion required
2. The magnitudes of the joint forces and moments
3. The interface pressures between the device and the patient

Question 4

What are the 3 segments which together form the lower limb? Also state what bones each segment is formed by

Answer 4

The three segments are the thigh, leg and the foot

The thigh is formed by the femur, the leg by the tibia and fibula and the foot by the tarsals, metatarsals and phalanges.

Question 5

What 3 major joints allow the 3 lower limb body segments to move relative to one another and the pelvic girdle?

Answer 5

The hip, knee and ankle joints

Question 6

What type of joints are the hip, knee and ankle joints ?

Answer 6

Synovial joints

Question 7

What holds together the hip, knee and ankle joints?

Answer 7

Muscles and ligaments

Question 8

What are the 2 main functions that joints of the lower limb are designed for ?

Answer 8

Movement and for weight bearing.

Question 9

What specific type of synovial joint is the hip joint ?

Answer 9

It is a ball and socket synovial joint

Question 10

What does a ball and socket joint comprise of and relate this specifically to the hip joint ?

Answer 10

It consists of the ball-shaped end of one bone fitted into a cup-shaped depression of another bone

In the hip joint, the ball consists of the head of the femur which fits into the socket-shaped acetabulum of the pelvic girdle

Question 11

What movements does the ball and socket shape of the hip allow the hip to move in ?

Answer 11

It allows the hip joint to rotate in three directions:

1. Flexion and extension
2. Abduction and adduction
3. Internal and external rotation.

It also allows the hip joint to circumduct

Question 12

Define what circumduction of the hip is

Answer 12

This is where the femur moves in a circle relative to the pelvis

Question 13

What type of joint are all the very mobile joints of the body which allow the major movements of the skeletal system?

Answer 13

Synovial joints - this includes the hip as one of the very mobile joints

Question 14

Describe the structure of a synovial joint

Answer 14

• The surfaces of the bones that form the joint are covered in articular cartilage; a low friction material.
• Synovial joints are enclosed in a sleeve of tough fibrous tissue, the joint capsule, which forms the synovial cavity
• The synovial cavity is filled with synovial fluid
• The synovial membrane lines the inner surface of the joint capsule.

Question 15

What is the function of synovial fluid

Answer 15

To lubricate the joint and provide nutrients to the articular cartilage.

Question 16

What is synovial fluid produced by ?

Answer 16

The synovial membrane

Question 17

What factors contribute to making the hip joint intrinsically stable and what do these factors also allow for?

Answer 17

• It is surrounded by a very strong articular joint capsule and several ligaments. These are surrounded by several large, strong muscles. These, along with its ball-and-socket shape all make it intrinsically stable
• These factors also allow for the wide range of movement required for common daily activities such as walking, sitting and squatting.

Question 18

Are hip dislocations common in adults ?

Answer 18

No - because of the stability of the hip joint they are very rare

Question 19

What are hip dislocations in adults usually caused by?

Answer 19

Serious road traffic accidents when very large impact forces are applied

Question 20

The hip joint has a wide range of movement in what planes ?

Answer 20

All three

Question 21

State the plane in whcih the range of motion of the hip joint is greatest and also state the movements of the hip which occur in this plane

Answer 21

• The sagittal plane
• The movements which occur in this plane are flexion and extension

Question 22

State the range of motion in degrees for flexion and extension of the hip

Answer 22

• Flexion ranges from 0 to about 140 degrees
• Extension ranges from 0 to 20 degrees.

Question 23

What movements of the hip joint occur in the frontal/coronal plane

Answer 23

Hip Abduction and adduction

Question 24

State the range of motion in degrees for abduction and adduction of the hip

Answer 24

• Abduction ranges from 0 to 30 degrees
• Adduction ranges from 0 to 25 degrees

Question 25

What movements of the hip occur in the transverse/ axial plane

Answer 25

Internal and external rotation

Question 26

State the range of motion in degrees for internal and external rotation of the hip

Answer 26

External rotation ranges from 0 to 90 degrees and internal rotation ranges from 0 to 70 degrees when the hip is flexed.

Question 27

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

Answer 27

Due to the restrictions of soft tissues

Question 28

To perform common daily activities, such as walking, standing up and sitting down, ascending and descending stairs, and stooping to pick up an object from the floor at least what degree of flexion-extension, abduction- adduction and rotation of the hip joint are required ?

Answer 28

• 120º of flexion-extension
• 20º of abduction-adduction
• 20º of rotation

Think all the 222 (emergency number in ninewells)

Question 29

Exactly what degrees of flexion-extension, abduction-adduction and rotation of the hip joint are required for standing up and sitting down in a chair?

Answer 29

• 110º of flexion-extension
• 20º of abduction-adduction
• 15º of rotation

Question 30

For walking what degrees of motion is required in all three planes in the hip joint i.e. flexion-extension (sagittal), abduction-adduction (coronal), internal-external rotation (transverse)

Answer 30

The most significant motion is in the sagittal plane with about 30º of flexion and 15º of extension. Only about 12º of the motion is required in the other two planes. (ab&adduction and rotation)

Question 31

Define what is meant by a bilateral and unilateral stance

Answer 31

• Bilateral stance = standing on two feet
• Unilateral stance = standing on one foot

Question 32

During bilateral stance are any of the hip muscles active ?

Answer 32

No - there are normally no muscles active at the hip joint.

Question 33

Why do we only need to consider the external forces acting on the hip joint during bilateral stance ?

Answer 33

Because there are normally no muscles active at the hip joint.

Question 34

What are the only 3 external forces acting on the pelvis

Answer 34

The weight of the upper body acting downwards and two reaction forces, one at each hip joint, acting upwards

(shown in pic - ingnore the fact it says unilateral stance in pic)

Question 35

What comprises the upper body?

Answer 35

The head, arms and trunk

Question 36

What percentage of total body weight does the upper body account for ?

Answer 36

70%

Question 37

What percentage of total body weight does the two lower limbs account for ?

Answer 37

30% - 15% per lower limb

Question 38

Do the worked example (wrote out in booklet) on pg. 114&115

Question 39

What can you conclude about the forces during normal bilateral standing acting on the hip joints ?

Answer 39

They are vertical and equal to half the upper body weight

Question 40

During unilateral stance what muscle activity is required to stabalise the position of the body?

Answer 40

Abductor muscle activity

Question 41

What 4 forces acting on the lower limb must be considered during unilateral stance?

Answer 41

1. The weight of the lower limb acting downwards
2. The abductor muscle force
3. The joint force at the hip
4. The ground reaction force acting vertically upwards on the foot.

Question 42

To simplify calculating the forces during unilateral stance what is done to the insertion point of the abductor muscles?

Answer 42

The insertion point is grouped to a single insertion point on the greater trochanter on the femur

Question 43

Do worked example pg. 115-119

Question 44

Is the hip joint force larger in unilateral or bilateral stance ?

Answer 44

It is larger in unilateral stance

Question 45

Why is the hip joint force a lot larger in unilateral stance compared to bilateral stance ?

Answer 45

• Most of the increase is due to the contraction of the hip abductor muscles which is required to stabilise the hip. The contraction of the hip abductor muscles effectively pulls the two sides of the hip joint together and, by doing so, it greatly increases the force at the hip joint.
• It is partially due to the fact that during unilateral stance only one hip is supporting the whole upper body rather than the two in bilateral stance