Mechanics: Unit 3 Lower limb (online) Flashcards
What produces synovial fluid?
synovial membrane
Why is the hip intrinsically stable?
it has a strong capsule, ligaments and is surrounded by large strong muscles
Which movement does the hip carry out in
a) sagittal plane?
b) frontal plane?
c) transverse plane?
a) flexion/extension
b) abduction/adduction
c) external/ internal rotation
In which plane of movement does the hip have the greatest ROM?
sagittal (flexion/extension)
How many degrees of flexion and extension is there at the hip?
flexion: 140
extension: 20
How many degrees of abduction and adduction is there at the hip?
abduction 30
adduction 20
How many degrees of rotation is there at the hip?
external 90
internal 70
How many degrees of each type of movement are required at the gip to perform activities of daily movement?
110 flexion/extension
20 abduction/adduction
15 rotation
How much of TBW is
a) upper body?
b) lower body?
a) 70%
b) 30%
In bilateral stance what forces must be considered at the hips?
external as no muscles are active ie. weight of upper body and 2 reaction forces
In bilateral stance what are the reaction forces equal to?
1/2 WHAT (weight of head, arms and torso)
What changes the forces at the hip during unilateral stance?
abductor muscles contract to stabilise the hip
Which forces must be considered at the hip during unilateral stance?
weight of the lower limb
abductor muscle force
joint force
ground reaction force
What is ground reaction force equal to?
equal and opposite of TBW
What are the two articulations of the knee joint?
tibiofemoral and patellofemoral
Which structures change the shape of the proximal tibia from flat to concave?
menisci
What are menisci?
crescent-shaped fibrocartilage that acts to aid stability of the knee, distribute the load and absorb shock
Describe the distal femur
2 condyes
trochlea
What does the trochlea become and what lies inside?
intercondylar notch
cruciate ligaments
What is a sesamoid bone?
a bone found inside a tendon
What is the largest sesamoid bone and where is it found?
patella
inside the quadriceps femoris tendon
What does the fibula do?
anchors biceps femoris muscle and the lateral collateral ligament
What movements do the cruciate ligaments prevent?
posterior movement of femur on tibia (sagging)
hyperextension of knee
What movements does the
a) medial collateral
b) lateral collateral
ligament prevent?
a) abduction
b) adduction
What sort of joint is the knee?
hinge joint but with changing axis of rotation
Describe how the knee joint’s centre of rotation changes in the sagittal plane as it flexes and extends.
semi-circular path due to condyle shape and restriction of ligaments
What does the screw-home mechanism describe?
the spiral motion of the knee joint as it flexes and extends in 3 planes because the medial condyle is longer than the lateral condyle
What movements does the knee allow for other than flexion and extension?
limited amount of ab/adduction and rotation
In which plane does the majority of knee motion occur and why?
sagittal plane due to tibiofemoral articulation
How much flexion and extension is there at the knee?
flexion 140
extension <5
How is the range of motion in the transverse plane dependent on the amount of flexion and extension?
almost zero at full extension, increases with flexion to a maximum at around 90° of flexion and reduces with further flexion.
due to interlocking of femoral and tibial condyles
What movements does the knee require for daily movement?
115 flexion
10 rotation
What is the main function of the patella?
It assists knee extension by increasing the lever arm of the quadriceps muscle force by displacing the quadriceps tendon.
When does the patella increase the lever arm of the quads muscle?
in full extension
What are the two main functions of the menisci?
shock absorb
distribute load across larger SA
When the menisci are removed how does this affect the stress in the joint tissues?
stress on point of contact
increases 3x
Which bones make up the ankle?
tibia, fibula and talus
What are the 3 articulations of the ankle?
distal tibiofibular
tibiotalar
fibulotalar
What is the
a) medial malleolus?
b) lateral malleolus?
a) bony prominence formed by tibia
b) bony prominence formed by fibula
What are the 3 main ligaments of the ankle joint?
anterior inferior talofibular
lateral ligament
medial ligament
What kind of joint is the ankle and what is the primary plane of movement?
hinge joint
sagittal
What point do we take the axis of rotation of the ankle joint from?
line between lateral and medial malleoli
What degree of dorsi and plantarflexion does the ankle joint allow for?
15 dorsi
30 plantar
How many bones and joints are there in the foot?
26 bones
57 joints
What comprises the hindfoot?
talus and calcaneous
What comprises the midfoot?
cuboid
cuneiforms
navicular
What comprises the forefoot?
metatarsals and phalanges
Between which two bones does the sub-talar joint lie?
talus and calcaneous
Which movement does the sub-talar joint allow for? to what degree?
20 degrees of inversion
5 degrees of eversion
Describe the arches of the foot
5 longitudinal from calcaneous to tarsals
1 transverse
Name the ligamentous structure which supports the longitudinal arches of the foot
plantar fascia
When is the plantar fascia put under tension?
when the toes dorsiflex
What is reciprocal gait?
lower limbs used alternatively to provide support and protection eg normal walking
How many steps in a gait cycle?
2
What is the stance phase of a gait cycle?
a foot in contact with the ground
What is the swing phase of a gait cycle?
a foot loses contact with the ground
What is double support?
when both feet are in contact with the ground
List the events that occur in reciprocal gait
heel contact flat foot mid stance heel off toe off mid swing heel contact
What step separates the two stages of the gait cycle
toe off
Which lower limb joint has the greatest range of motion during reciprocal gait?
the knee
What is a ground reaction force?
the equal and opposite force the ground exerts when the foot exerts a force on the ground
What causes the first vertical peak of ground reaction force?
deceleration of body weight as weight transfers on to foot
What causes the second vertical peak of ground reaction force?
foot pushes off the ground
Why do hip extensors contract after heel contact?
extension prevents body from falling forward
Why do the hamstrings contract at heel contact?
cause a small flexion to prevent hyperextension
Why does plantar flexion increase just before toe off?
as triceps surae contracts to push the foot up and off the ground
Describe the anatomy and function of the plantar fascia.
anatomy:
extends from os calcis to phalanges
ligamentous structure
function:
shock absorber
supports longitudinal arches + prevent them collapsing due to downward forces at ankle
joint bones of foot so they move as one when the toes dorsiflex
Which lower limb joint has the least range of motion during reciprocal gait?
the ankle
What is the range of motion at the hip during reciprocal gait?
30 flexion to 15 extension
When does hip flexion peak during reciprocal gait? Why?
shortly after mid- swing to ensure a long step
When does hip extension peak during reciprocal gait?
before toe off as leg is left trailing behind
What is the range of motion at the knee during reciprocal gait?
from a few degrees to 70 degrees of flexion
When does knee flexion peak during reciprocal gait? Why?
during the swing phase as the knee is flexed to allow the foot to clear the ground as it swings past the other limb
What is the range of motion at the ankle during reciprocal gait?
15 degrees of plantarflexion to 10 degrees of dorsiflexion
When does peak ankle dorsiflexion occur? why?
heel off as the foot is left trailing behind the rest of the body.
When does peak ankle plantarflexion occur?
toe off, flat foot
