Biomech unit 3 SAQ's Flashcards
Name the three segments of the lower limb
The thigh, leg and foot
Name the three major joints of the lower limb
The hip, knee and ankle.
State the two functions of the joints of the lower limb.
Movement and weight bearing.
What type of joint is the hip joint?
The hip joint is a ball-and-socket type synovial joint.
What are the two functions of synovial fluid?
Synovial fluid lubricates the joint and provides nutrients to the articular cartilage.
Why is the hip joint intrinsically stable?
The hip joint is intrinsically stable due to its shape (ball and socket), its strong joint capsule and the surrounding ligaments and muscles.
In which plane does the greatest range of motion of the hip joint occur?
In the sagittal plane (flexion-extension)
Typically, what range of motion is required at the hip joint to stand up and sit down?
- Typically around 110° of flexion-extension
- 20° of abduction-adduction
- 15° of rotation is required to stand up and sit down.
How does abductor muscle activity affect the hip joint force during unilateral stance as compared to bilateral stance?
- 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.
Name the two articulations that comprise the knee joint.
- Tibiofemoral
- Patellofemoral
What type of bone is the patella?
The patella is a sesamoid bone.
What gives the knee joint its stability?
The stability of the knee joint is derived from its ligaments, in particular the cruciate and collateral.
Describe how the knee joint’s centre of rotation changes in the sagittal plane as it flexes and extends.
The knee joint’s centre of rotation in the sagittal plane follows a semicircular path as it flexed and extended.
What does the screw-home mechanism describe?
The screw-home mechanism describes the spiral motion of the knee joint as it flexes and extends.
In which plane does the majority of knee motion occur?
The sagittal plane
How is the range of motion in the transverse plane dependent on the amount of flexion and extension?
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.
During standing up how will the amount of motion in the sagittal plane be affected when the height of the chair is lowered?
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.
Classify the lever system shown in the pic
fulcrum located between the effort force and resistance force, it is therefore a first class lever.
Is the quadriceps femoris muscle working at a mechanical advantage or a mechanical disadvantage?
The lever arm for the quadriceps femoris muscle is less than that for the resistance force, it is therefore acting at a mechanical disadvantage.
What are the two main functions of the menisci?
The two main functions of the menisci are distribute the force more evenly and to absorb large force peaks
When the menisci are removed how does this affect the stress in the joint tissues?
When the menisci are removed the stress in the joint tissues is increased by approximately three times.
Name the bones that form the ankle joint.
The bones that form the ankle joint are the tibia, fibula and talus.
How many articulations are there in the ankle joint?
3
Name the three main ligaments that stabilise the ankle joint.
The three main ligaments that stabilise the ankle joint are the anterior inferior talofibular, the medial and lateral ligaments.
What is dorsiflexion?
Dorsiflexion is flexion of the ankle joint - toes move upwards.
What is plantarflexion?
Plantarflexion is extension of the ankle joint - toes move downwards.
What are the three parts of the foot called and which bones make up each part?
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.
Name the bones that form the subtalar joint.
The talus and the calcaneus bones
What movements occur at the subtalar joint?
Inversion and eversion of the foot
Name the ligamentous structure which supports the longitudinal arches of the foot.
The plantar fascia
What is reciprocal gait?
- Reciprocal gait is the gait most commonly used for walking.
- During reciprocal gait the lower limbs are used alternatively to provide support and propulsion.
What is gait analysis?
Gait analysis is the examination of gait.
What type of equipment is contained in a gait laboratory?
A motion analysis system, force plates and electromyography equipment.
What is a motion analysis system?
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.
During reciprocal gait, what defines the stance phase and the swing phase?
- 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
What is double support?
It is the period during the gait cycle when both feet are in contact with the ground.
List the events that occur in reciprocal gait.
- Heel contact
- Foot flat
- Mid stance
- Heel off
- Toe off
- Mid swing
Which lower limb joint has the greatest range of motion during reciprocal gait?
Knee joint
When does the peak amount of dorsiflexion occur during the gait cycle?
Around heel off
What is a force plate used to measure?
The ground reaction force exerted on the foot during the stance phase of gait
Why do the hamstrings contract at heel contact?
The hamstrings contract slightly at heel contact to prevent the hyperextension of the knee.
