Article Flashcards
what is kinetics
the study of forces that cause motion
(forces, torques)
“the study of forces associated with motion using force plates, pressure platforms and/or inshoe sensors providing a direct description/orientation of foot posture”
what is kinematics
the study of describing movements
(velocity, acceleration)
“related to the measurement of motion irrespective of the forces involved using cameras to observe the intersegmental relationship of the trunk and limbs”
what is the role of the human foot
provides support and balance during standing
stabilises the body during gait
what does the foot have to do during stance phase (between heel strike and toe off)
to adapt to a changing patter of loading as the centre of mass of the body moves
what is the GRF
ground reaction force
equal and opposite reaction when the foot comes into contact with the ground
changes in direction and magnitude as the body propels itself forwards
what are the important mechanical structures of the foot
3 things
1 - the bony skeleton, which together with the ligaments and arches, provides relative rigidity and lever arm mechanism required to maintain balance
2 - joints which allow felxibility
3 - muscle and tendons which control foot movement
what does the foot need to do during the stance phase and what does failure to do so lead to
distribute and dissipate compressive, tensile, shearing, and rotatory forces
failure can lead to abnormal movements which produces excessive stress which can result in the breakdown of soft tissue and muscle
how many bones are in the foot
26
- 7 tarsals
- 5 metatarsals
- 14 phalanges
how many joints are in the foot
6
- ankle
- subtalar
- midtarsal
- tarsometatarsal
- MTP
- IP
what are the 4 segments of the foot
hindfoot
midfoot
forefoot
phalanges
what does the hindfoot consist of
talus
calcaneus
what is the function of the talus bone
orientated to transmit reactive forces from the foot through the ankle joint to the leg
lies between the calcaneus and tibia
what is the function of the calcaneus
largest and most posterior bone in the foot and provides a lever arm for the insertion of the Achilles tendon
what muscles acts through the achilles tendon and what do they do
gastrocnemius and soleus
impart powerful plantarfexion forces to the foot
what does the height, width and structure of the calcaneus allow it to do
withstand high tensile, bending and compressive forces on a regular basis w/out damage
what makes up the midfoot
navicular, the cuboid and three cuneiforms
what is the main role of the navicular bone
is the keystone for the medial longitudinal arch
what is the function of the cuneiforms
articulate with the first, second and third metatarsals distally
contribute to stability of midfoot
what makes up the forefoot
5 metatarsals
how is the first metatarsal different from the others
is the shortest and widest
how does the second metatarsal compare to the first
extends beyond the first
what is the second metatarsal so important
articulates with the intermediate,medial and lateral cuneiforms in a ‘key-like’ configuration which promotes stability
makes it the stiffest and most stable portion of the foot playing a key role in stabilizing foot posture after hallux surgery.
why attaches to the styloid, laterally and proximally on the fifth metatarsal and what injury can happen here as a result
the peroneus brevis tendon inserts
Avulsion # of the styloid commonly occurs when the foot is inverted against the contracting peroneus brevis muscle
what do the toes (phalanges) contribute to
weight bearing and load distribution
propulsion during the push-of phase of gait.
what are the 3 planes of motion in joints
sagittal plane
frontal (coronal) plane
transverse
what joints of the foot have one degree of freedom (i.e. only move in one plane)
subtalar
ankle
tarsometatarsal
what joints of the foot have two degree of freedom (i.e. move in two plane) and what are the 2 planes
midtarsal
MTP
IP joints
adduction-abduction
dorsiflexion-plantarflexion
what does the ankle joint consist of and what motion does it allow
articulation between distal part of the tibia and the body of the talus
dorsiflexion and plantarflexion
what is the ROM need at the ankle joint for normal locomotion
10 degrees of dorsiflexion
20 degrees of plantarflexion
why is there instability in the ankle joint during plantarflexion
has slight movement in transverse plane during plantarflexion
causing instability of the joint in this position
what is included in the subtalar joint
the talocalcaneal joint and the talocalcaneal part of the talocalcaneonavicular joint
at what degree does the axis of motion pass through the subtalar joint
42 degrees from the Transverse plane and 16 degree from the sagittal plane
what are the motions permitted at the subtalar joint
supination
pronation
what together forms the midtarsal joint
The talonavicular and the calcaneocuboid joints
what are the two axis of motion of the midtarsal joint and what motion does it contribute to
oblique axis
longitudinal axis
pronation/supination
what is the ROM at the MTP joint
up to 90 degrees extension
only few degrees flexion
what is ROM for IP joints
allow extension (related to abduction)
allow flexion (related to adduction)
what is the medial arch comprised of
the calcaneus, talus, navicular, the three cuneiforms and their three metatarsals
what are the pillars of the medial arch
tuberosity of the calcaneus posteriorly
heads of the medial three metatarsal bones anteriorly
what is the lateral arch comprised of
calcaneus, the cuboid and the lateral two metatarsals
how does the tension in the MA and LA change during walking
relatively rigid in standing but become more compliant during walking; the MA being the more flexible of the two
there is also a series of transverse arches - where are they centered round
the MTP joints
- form a convex curve in the direction of the dorsum
what happens to the TA’s during walking
disappear and flatten to varying degrees during weight bearing
what supports the integrity of the arches
ligaments (particularly in LA)
muscles (particularly in MA)
tendons
provide strength, flexibility and movement.
what are the two groups of muscles operating on the foot
extrinsic muscles - from lower leg
intrinsic muscles - within foot itself
what is the function of the muscles during locomotion
provide stability and balance during standing
and a strong lever arm effect during propulsion
what are most of the problems associated with foot disorders related to
the weight bearing process at the foot-ground or foot/shoe-ground interface
what is the reference for one full gait cycle (GC) and what is the time interval known as
time interval between two consecutive heel strikes of the same foot on the ground
time interval known as stride time
stages of GC
heel strike forefoot loading midstance heel off toe off
what are the 2 phases of GC
stance phase (60%) swing phase (40%)
what is double support in GC
when both feet are in touch with the ground
lasts 10% of GC and occurs twice in any GC
what counteracts the GRF
function of the lower limb muscles in conjunction with bones, joints and tendons of the foot
what is the function of lower limb muscles during gait
to stabilise and accelerate/decelerate the foot during both wt bearing and propulsion
some muscles in lower limb have more than one function - what roles does the long extensors have
- stabilise the joints of the toes during propulsion
- serve as accelerators in ankle joint dorsiflexion following toe off
- assist as decelerators of the foot at HS
some muscles in lower limb have more than one function - what roles does the tibialis anterior have
- decelerates the foot following HS
- accelerates to assist in ankle joint dorsiflexion following TO.
what occurs very shortly after HS
transient period
- GRF is anterior to both ankle and knee joint
- lasts between 10 and 20ms
how does the location of the GRF change after HS and what does this create
changes to a location posterior to both joints (ankle and knee)
creates an external plantarflexion moment around the ankle joint
what happens instantaneously when this external plantarflexion moment occurs
the tibialis anterior and the extensor hallucis longus muscle contract eccentrically
producing an internal dorsiflexion moment which decelerates the rate of ankle joint plantarflexion
what does the combo of the external plantarflexion moment and the internal dorsiflexion moment allow
synergistic action of these two muscle groups allows the foot to passively plantarflex in a smooth, regulated manner
ankle joint plantarflexion is virtually stopped synchronously with the forefoot making contact with the ground.
how is the subtalar joint, ankle and leg positioned during HS
subtalar - inverted
ankle - dorsiflexed
leg - internally rotated
what time delay was observed in the tibialis anterior in diabetic patients and what does this mean
180ms
late firing means normal modulating role of the muscle in lowering foot to the ground after HS is disturbed
leads to forefoot slap and high plantar pressure
during initial movement, what is the only part of the forefoot that makes contact with the ground and what happens as weight is transferred
the lateral side of the forefoot
as wt transferred to the forefoot, the effect of the GRF on the lateral side tends to evert the forefoot against resistance caused by contraction of TA
what does controlled relaxation of TA facilitate
smooth progressive loading of the forefoot from lateral to medial locations
GRF can evert the forefoot until full foot contact is achieved and loading is then transferred from lateral to medial side
what happens after HS but before forefoot contact
the calf muscles, i.e. the tibialis posterior, soleus and gastrocnemius, begin to contract
what do the calf muscles work to do
function to collectively decelerate subtalar joint pronation and internal leg rotation
continue to contract throughout MS phase
relax at HO
what happens to GRF during forefoot loading
GRF maintains its posterior direction but w/ increasing magnitude until MS
it then moves anteriorly along the foot - causes GRF to become smaller and ultimately reverse in direction [i.e. still posterior to the knee joint but now anterior to ankle joint]m
what happens at the beginning of the MS period
the posterior calf muscles become prime movers which initiate subtalar joint supination and external leg rotation.
Both the TP and soleus have attachments which create significant lever arms relative to the axis of motion of the subtalar joint.
what happens in relation to ankle after forefoot contact
the ankle is plantarflexed, and following this, the ankle joint begins to dorsiflex as the tibia moves forwards, over the foot.
tibia continues to move forward causing ankle joint dorsiflexion throughout MS period until point of HO
what does deceleration of forward tibial momentum also do
extend the knee in preparation for HO
[muscles which decelerate the forward momentum of the tibia to assist in knee extension are those which have significant lever arms for ankle joint plantarflexion]
what are the muscles that decelerate the forward momentum of the tibia/ have significant lever arms for ankle joint plantarflexion
[muscle that is also ankle joint plantarflexor]
tibialis posterior, soleus, and flexor digitorum longus
[gastrocnemius]
what stabilises the lesser tarus during the MS period and how do they do this
in early MS
- soleus, tibialis posterior, peroneus longus, and peroneus brevis muscles
soleus
- maintains the Sp stability of the cuboid in order to serve as an effective pulley for the function of peroneus longus
peroneus longus
- pulls the first ray laterally against the lesser tarsus
TP
- pulls the lesser tarsal bones medially.
overall effect
- compresses the lesser tarsus in the Tp, thus producing medio-lateral stability
how does the peroneus brevis complement the function of peroneus longus to help in maintaining transverse stability of the lesser tarsus during stance phase
the magnitude of the adduction force generated by TP exceeds that of the abduction force exerted by the peroneus longus.
peroneus brevis exerts an additional abduction force upon the lesser tarsus to thereby neutralize the otherwise existing imbalance.
when the foot is fully pronated what facilitates further abduction
pronation of the subtalar joint
[in CP, entire foot may be pronated into a flat foot position, called peroneal spastic flatfoot]
at HO, where is the GRF and what does it cause
anterior in relation to both ankle and knee joints creating an external dorsiflexor moment which is opposed by both the soleus and gastrocnemius muscles
what happens following HO in regards in terms of wt bearing and what happens simultaneously
foot momentarily bears full body weight alone
the vertical GRF generated exceeds that of bodyweight and the ball of the foot is also subjected to torque and high shear forces.
what is the major function of the intrinsic muscles during second half of MS phase
provide the tensile forces necessary to stabilise the bones of the metatarus and lesser tarus transversely and posteriorly against one another.
[when foot is abnormally pronated the IM muscles must function longer and stronger]
what interaction allows for the action of heel rise
interaction between forward momentum of the body, deceleration of the tibia, and passive knee flexion
what happens at the end of MS
the trunk is directed forwards relative to the foot, and the body is falling forwards over the weight-bearing foot.
Forward trunk momentum carries the thigh and leg with it
what does the knee do immediately prior to heel rise and what does the tibia do thereafter
begin to flex
tibia continues to move forward while the heel rises, maintaining ankle dorsiflexion into the early propulsion period
what muscles are responsible for tibia deceleration
TP, gastrocnemius and soleus with later assistance from the FDL and peroneus longus
what halts knee extension just before heel rise
contraction of the gastrocnemius muscle
what does the ankle do during propulsion phase
initially dorsiflexes slightly and then plantarflexes until TO
Shortly after heel rise, ankle dorsiflexion is stopped consequent to the weight no longer passing through the heel
calf muscles then plantarflex ankle
during the early stage of propulsion, what muscles are contributing to ankle joint plantarflexion
gastrocnemius, soleus, peroneus longus
transverse pedis - transverse stabiliser of the forefoot.
what happens shortly after heel rise and what muscles are involved
the lateral side of the foot lifts from the ground
weight is transferred to the medial side of forefoot where it concentrates on the great toe
peroneus longus and brevis
The long and short plantarflexors of the lesser digits stabilise the toes against the ground - but they cannot do so unless what
toes are converted into rigid beams by extensor mechanism.
what factors influence propulsion phase stability of the great toe
stability and plantarflexion of the first ray
normal sesamoid function
normal strength and function of the muscles responsible for hallux, and first MTP joint stability.
what movement must the hallux be able to do during final propulsion
65-70 degrees of dorsiflexion on the first metatarsal
or it will sublux at the first MTP joint and become unstable
where is GRF just prior to toe off
anterior to the ankle and posterior to the knee
what happens immediately before TO and what does this create
tibialis anterior begins to contract (until mid swing)
creates a smaller dorsiflexor moment around the ankle joint which helps in clearing the foot off the ground
what is an issue with gait analysis labs
have not proven to be cost effective
what is problems facing analysis in gait labs
type of analysis dependant on type of equipment and expertise of used
up to 1 and a half hour needed per subject to record gait data
what is GaitRite
portable gait analysis system,
relatively cheap, easy to use and provide an almost complete analysis instantaneously
what conditions is GaitRite useful for
“shuffling gait” and those with low assessment tolerance
e.g. Parkinson’s disease
disadvantage of GaitRite
incompetent in providing inter-segmental relationship
crucial in patients with CP
devices that are add-ons to measuring gait and pressure
portable electromyography
goniometry
energy expenditure.
what does measuring pressure tell you
gait cycle pressure points gait pattern foot print and posture centre of pressure
what is foot/ankle proprioception
awareness of the position and motion of the foot joints in space with the ability to accurately match reference joint angles without visual feedback
how many injuries resulting in time lost through injury in running and jumping sports involve the ankle
20-25%
in ruptures of the fibular collateral ligament, what was functional instability suggested to be
mechanical instability
peroneal weakness
tibio-fibular strain and proprioceptive deficit
what are pilon fractures and how does it occur
fracture of distal part of the tibia involving the articular surface of the ankle
result of an axial loading injury which drives the talus into the tibia
what foot movements lead to injury
internal rotation
external rotation
abduction
adduction
extrinsic risk factors for the ankle
training errors, type of activity (e.g. sport), exercise time, equipment and environmental conditions
intrinsic risk factors for the ankle
height, weight and previous Hx of ankle sprain = lateral ankle sprain
muscle strength imbalance = eversion-to-inversion strength ratio and greater plantarflexion strength = higher incidence of inversion ankle sprain
Ankle injuries are fewer in unshod populations - what does this suggest
shoes may alter the ability of the protective mechanisms around the ankle in preventing damage
may be due to increased leverage at the ankle confirmed by the unnatural high heel and reduction of foot/ground sensation
what shoes had a 123% greater injury frequency of the lower limb compared to cheap shoes
expensive athletic shoes to that advertised safeguard feet through ‘cushioning impact’
what is general rules for treating a patient
Avoid Trial and Error Management
Always try to find the primary cause of the problem
Never treat the secondary symptoms without
knowing the primary cause
what can form as the results of friction with the inner shoe
dorsal callus formation
what causes damage in high heel shoes
forward shift of the centre of mass
- results in increased pressure under the metatarsal heads and toes
- results in abnormal joint and muscles function within the foot and lower leg
- results in ultimately abnormal balance, proprioception and body posture
what are the Sx that high heels cause
damage to calf muscles
painful knees and strained back muscles
enlarged joints
damage to soles and arches
hard skin/corns/bunions
deformed toes
what question can you ask the patient to find out if the shoes are causing the pain
do you get the same pains when you walk barefooted?
what is a compensatory measure for push off from the forefoot seen after shortening of the first rays (case B)
higher pressure values under the lesser toes
why did a dome/button insole not work with the women with shortening of the first rays (case B)
elevated the 2nd, 3rd and 4th metatarsal shafts which further extended the lesser toes and in turn increased the pressure under them
what was done for the women w/ increased pressure under her lesser toes (case B)
1 - transverse rocker that facilitates the transfer of load from the lateral to medial aspects of the foot
2- longitudinal rocker compensates for the first ray shortening and assists at the push off stage
what did wearing shoes smaller than the patients right foot cause (case C)
caused abnormal longitudinal forces along the first ray in addition to the irritation caused by the built-in arch
problem was localised around the mid-pt of the flexor hallucis longus (FHL)
