Biomech unit 3 SAQ's

Question 1

Name the three segments of the lower limb

Answer 1

The thigh, leg and foot

Question 2

Name the three major joints of the lower limb

Answer 2

The hip, knee and ankle.

Question 3

State the two functions of the joints of the lower limb.

Answer 3

Movement and weight bearing.

Question 4

What type of joint is the hip joint?

Answer 4

The hip joint is a ball-and-socket type synovial joint.

Question 5

What are the two functions of synovial fluid?

Answer 5

Synovial fluid lubricates the joint and provides nutrients to the articular cartilage.

Question 6

Why is the hip joint intrinsically stable?

Answer 6

The hip joint is intrinsically stable due to its shape (ball and socket), its strong joint capsule and the surrounding ligaments and muscles.

Question 7

In which plane does the greatest range of motion of the hip joint occur?

Answer 7

In the sagittal plane (flexion-extension)

Question 8

Typically, what range of motion is required at the hip joint to stand up and sit down?

Answer 8

• Typically around 110° of flexion-extension
• 20° of abduction-adduction
• 15° of rotation is required to stand up and sit down.

Question 9

How does abductor muscle activity affect the hip joint force during unilateral stance as compared to bilateral stance?

Answer 9

• Muscle activity generally increases the magnitude of the joint forces by pulling the two sides of the joint together.
• During unilateral stance the contraction of the hip joint abductors acts in this way, causing a large increase in the joint force as compared to bilateral stance when there is usually no muscle activity.

Question 10

Name the two articulations that comprise the knee joint.

Answer 10

1. Tibiofemoral
2. Patellofemoral

Question 11

What type of bone is the patella?

Answer 11

The patella is a sesamoid bone.

Question 12

What gives the knee joint its stability?

Answer 12

The stability of the knee joint is derived from its ligaments, in particular the cruciate and collateral.

Question 13

Describe how the knee joint’s centre of rotation changes in the sagittal plane as it flexes and extends.

Answer 13

The knee joint’s centre of rotation in the sagittal plane follows a semicircular path as it flexed and extended.

Question 14

What does the screw-home mechanism describe?

Answer 14

The screw-home mechanism describes the spiral motion of the knee joint as it flexes and extends.

Question 15

In which plane does the majority of knee motion occur?

Answer 15

The sagittal plane

Question 16

How is the range of motion in the transverse plane dependent on the amount of flexion and extension?

Answer 16

The range of motion in the transverse plane is almost zero at full extension, increases with flexion to a maximum at around 90° of flexion and reduces with further flexion.

Question 17

During standing up how will the amount of motion in the sagittal plane be affected when the height of the chair is lowered?

Answer 17

If the height of the chair is lowered then the range of knee joint motion required in the sagittal plane will be increased since the knee will start at a position of greater flexion.

Question 18

Classify the lever system shown in the pic

Answer 18

fulcrum located between the effort force and resistance force, it is therefore a first class lever.

Question 19

Is the quadriceps femoris muscle working at a mechanical advantage or a mechanical disadvantage?

Answer 19

The lever arm for the quadriceps femoris muscle is less than that for the resistance force, it is therefore acting at a mechanical disadvantage.

Question 20

What are the two main functions of the menisci?

Answer 20

The two main functions of the menisci are distribute the force more evenly and to absorb large force peaks

Question 21

When the menisci are removed how does this affect the stress in the joint tissues?

Answer 21

When the menisci are removed the stress in the joint tissues is increased by approximately three times.

Question 22

Name the bones that form the ankle joint.

Answer 22

The bones that form the ankle joint are the tibia, fibula and talus.

Question 23

How many articulations are there in the ankle joint?

Answer 23

3

Question 24

Name the three main ligaments that stabilise the ankle joint.

Answer 24

The three main ligaments that stabilise the ankle joint are the anterior inferior talofibular, the medial and lateral ligaments.

Question 25

What is dorsiflexion?

Answer 25

Dorsiflexion is flexion of the ankle joint - toes move upwards.

Question 26

What is plantarflexion?

Answer 26

Plantarflexion is extension of the ankle joint - toes move downwards.

Question 27

What are the three parts of the foot called and which bones make up each part?

Answer 27

The three parts of the foot are the forefoot, the midfoot and the hindfoot. The forefoot is made up of the metatarsals and phalanges. The midfoot is made up of the cuniforms, the cuboid and the navicular. The hindfoot is made up of the talus and calcaneus.

Question 28

Name the bones that form the subtalar joint.

Answer 28

The talus and the calcaneus bones

Question 29

What movements occur at the subtalar joint?

Answer 29

Inversion and eversion of the foot

Question 30

Name the ligamentous structure which supports the longitudinal arches of the foot.

Answer 30

The plantar fascia

Question 31

What is reciprocal gait?

Answer 31

• Reciprocal gait is the gait most commonly used for walking.
• During reciprocal gait the lower limbs are used alternatively to provide support and propulsion.

Question 32

What is gait analysis?

Answer 32

Gait analysis is the examination of gait.

Question 33

What type of equipment is contained in a gait laboratory?

Answer 33

A motion analysis system, force plates and electromyography equipment.

Question 34

What is a motion analysis system?

Answer 34

A motion analysis system is a device which records the motion of markers placed on a patient, thus allowing the patient’s movements to be reconstructed and observed on a computer.

Question 35

During reciprocal gait, what defines the stance phase and the swing phase?

Answer 35

• Stance phase defined as the phase when the foot is in contact with the ground so from heel contact to toe off of e.g. the right foot
• Swing phase is defined as the phase in which the foot is not in contact with the ground so from toe off to heel contact of e.g. the right foot

Question 36

What is double support?

Answer 36

It is the period during the gait cycle when both feet are in contact with the ground.

Question 37

List the events that occur in reciprocal gait.

Answer 37

1. Heel contact
2. Foot flat
3. Mid stance
4. Heel off
5. Toe off
6. Mid swing

Question 38

Which lower limb joint has the greatest range of motion during reciprocal gait?

Answer 38

Knee joint

Question 39

When does the peak amount of dorsiflexion occur during the gait cycle?

Answer 39

Around heel off

Question 40

What is a force plate used to measure?

Answer 40

The ground reaction force exerted on the foot during the stance phase of gait

Question 41

Why do the hamstrings contract at heel contact?

Answer 41

The hamstrings contract slightly at heel contact to prevent the hyperextension of the knee.