wk 3- theories Flashcards
what can force cause
motion or deformation of a mass
equation for force
F= mass x acceleration
force has what, which explains what reaction
equal and opposite reaction, explains ground reaction force
define stress
intensity of internal forces within an object or the ability to develop internal resistance to loading force
stress equation
S= force / cross sectional area
larger cross sectional area for stress means?
it can withstand higher amounts of stress and vice versa
define pressure
force applied perpendicular to unit surface area
pressure equation
P= force/area
higher pressures are caused by
smaller surface areas
define strain
relative amount of deformation of an object when it is subjected to load
the change in length
strain equation
difference in length
what is elastic deformation
initial part of strain when it can bounce back to its original length (reversible)
what is plastic defamation
second part of strain when tears occur and the material cannot go back to original length (irreversible)
exceeding what will cause rupture in material (plastic defamation)
ultimate tensile strength
what are 3 issues with roots theory
- Reliability of measurement (bisections, ROM, soft tissue movement)
- Criteria too stringent for normal foot alignment - majority have a deformity
- Position of STJ during walking
what is tissue stress model
injury occurs if the mechanical stresses acting on the tissue is beyond the tolerance of the tissue. Treatment is directed at reducing the load and increasing tissue capacity. Injury is NOT caused by intrinsic deformities.
stress on tissues can cause 3 responses
- Elastic region (reversible, normal give and take)
- Plastic region (overuse injuries, damages to tissues)
- Biological response to stress (wolf and davies laws, remodelling due to stresses)
types of stresses
- Axial (compressive-squashed and tensile-lengthened)
Compressive: bone, plantar foot muscles
Tensile: tendons, ligaments, muscles - Shear (friction)
Between structures (layers of the skin, joints, uneven muscle fibres, insetion of tendon to bone- attachments arent always perpendicular and often on angles)
loading patterns can be
- Bending- compressive and tensile stresses on opposite sides
Metatarsals during propulsion - Torsion- shear stresses, greatest at the edge
Jones fractures.
what type of stresses does plantar fascia take
compressive (ground)
tensile (conteract pronation)
shear (attachment to calc)
4 steps to assessment and managing stress related pathology
- Identify tissues being excessively stressed
Based on history, symptoms (NILDOCART), what is the patients goal, Come up with initial Dx (skin to bone)
- Application of controlled stresses
Weight bearing, non weight bearing, palpation, ROM, function/strength assessments
Allows you to develop a working diagnosis and rule out other diagnoses
- Evaluate findings
Is the cause secondary to mechanical loading?
Assess the structure: what is its action during the activities when it hurts, what stresses are involved, can stresses be elevated, do the tissues have reduced capacity to withstand stress?
- Institute a management protocol
Reduce stress to a tolerable level (rest, footwear, foot orthoses)
Healing the involved tissue (soft tissue modalities like ice, shock wave, compression)
Restoration of flexibility and strength (increase stress capacity of tissues, exercises)
- Monitor, evaluate and adjust treatment plan
challenges of TSM
- measurement (no way to measure the tissue stresses, other than compressive stress through plantar pressures)
We dont know if interventions reduce stress - Unclear link between assessment and orthosis prescription (roots theory goes off normal positions, stress model targets reducing stress in areas- more freedom in choosing orthotic prescriptions but more complicated)
- Doesn’t explain how the foot functions (not useful for prevention)
strengths of TS model
- Outcome measure (treatment guided by symptoms reduction, functional improvement and meeting patient goals) instead of changing their foot to normal like roots theory (kinematic change)
- Multifaceted approach (foot orthosesis may be part of treatment, not limited to custom made and incorporates other therapies like exercises)
what is sagittal plane facilitation of motion theory
3 rockers in the sagittal plane, heel, ankle and 1st MTPJ that facilitate motion (70% of motion). if there is a block in any of these rockers, the body compensates to push through or around it
what compensations can be visualised if theres blocks in one of the rockers
-early heel lift (more pressure and load in forefoot)
-vertical toe off (more hip dominate in gait)
-abducted or adducted toe off (to roll over the foot)
-energy into loading the tissue more
what are the 3 autosupport mechanisms of SPFM
- Calcaneocuboid locking- secondary to tightening of the plantar fascia
Stabilisation of rearfoot and midfoot with joint locking prior to heel lift - Windlass mechanism
DF of the hallux pulls on the plantar aponeurosis, shortening the distance between the met heads and calc - Closed packing of bone
Fascial tightening and locking wedge effect
Final piece of stabiliation process and foot can now resist highly repeititve loads
what could cause a lack of heel rocker
- trauma
- neurological conditions (foot drop)
what could cause a lack of ankle rocker
- ankle equinas (soft tissue or bone)
- forefoot equinas
- ankle stiffness
what could cause a lack of forefoot rocker
- hallux ROM decreased
- functional hallux limitus
- windlass function
compensations/consequences of ankle restriction
Steppage gait (vertical toe off)
Early heel lift (bouncy gait)
Midfoot pronation
Shorter step length
Increased genu recurvatum and increased lumbar lordosis (COP forward)
Extensor substitution
Unstable MTJ
compensations/consequences of 1st MTPJ restriction
- Altered heel lift, a delay in the heel because midfoot pronation occurring to compensate for lack of ROM in MPJ
- Vertical toe off, foot lifted off the ground (steppage gait)
- Inverted step, COP deviated laterally to shift the area of toe off
- Abducted and adducted toe off, a twist
- Flexion compensation at the torso, knee, head
treatment interventions for heel rocker
- surgery
- footwear modification (heel rocker sole, heel raises)
- bracing
treatment interventions for ankle rocker
- stretches
- manual therapy
- heel raise
- surgery
treatment for forefoot rocker
- allow 1st ray plantarflexion (1st ray cut out, mortons reverse extension, cluffy wedge, casting technique)
- rocker sole
what is functional hallux limitus
functional inability of the proximal phalanx to extend on the 1st metatarsal head (DF 20-30deg). Full range of motion non weightbearing.
