Chris' Theories Of Foot Function

Question 1

name the theories of foot function chris outlined [5]

Answer 1

root, tissues stress theory, preferred movement pathway, sagittal plane facilitation, rotational equilibrium

Question 2

briefly describe root theory

Answer 2

• bisector of the distal 1/3 of leg
• STJ neutral
• calc bisector vertical
• MTJ max pronation
• min 10 degrees DF @ AJ
• minimal muscle activity required when foot is in this “ideal stance position” –> as we stray from this things go to shit

Question 3

briefly outine tissue stress theory (McPoil & Hunt 1995)

Answer 3

elastic region = normal stress/ok
plastic region = injury/pathology/sx
“microfailure” zone” in between this is were pathology happens at a cellular level but nothing clinical (yet)
–> we want to keep our tissue in a zone of optimal stress without exposing other tissues to undue stress

Question 4

explain the implications for our clinical practice of tissue stress theory

Answer 4

• to reduce tissue stress we need to get the tissue back to the elastic region of the load-deformation curve
• also be mindful: after injury (where there has been “permanent damage” to the tissue) the mechanical properties of the soft tisse have altered and the soft tissue is now less resilient to application of load

Question 5

outline what Nigg was on about with the “preferred movement pathway”

Answer 5

based on theory that movement is controlled by muscles and the activity of muscles can be modified

1. muscle tuning: all muscles can be tuned which, once done correctly can dissipate impact forces applied to the body
2. preferred motion pathway : the way the body adapts (which can be influenced by ‘tuning muscles’ must match the preferred pathway of movement

Question 6

outline what is meant by the sagittal plane facilitation theory (Dananberg)

Answer 6

basically we want to have most of our motion in the sagittal plane in propulsion
- restricted ROM of hallux = functional hallux limitus –> results in compensatory gait patterns e.g. early heel lift, MTJ can’t lock –> increased arch deformation, inefficient windlass mechanism, potential lateral column loading, increased transverse plane motion during prop

Question 7

explain the clinical implications of sagittal plane facilitation theory (Dananberg)

Answer 7

• probs can be applied to the entire stance (not just propulsion)
• we want to minimise out of SP influences on foot function i.e. OPTIMISE SP to be more efficient

Question 8

outline what is meant by rotational equilibrium

Answer 8

• clockwise should be = to anticlockwise moments
• joint should either be rotating at a constant velocity or not rotating (i.e. try to load tissue slow/gradual)
• antag/agonist balance important

Question 9

name the 4 key components of chris’ theory for gait analysis

Answer 9

1. do NOT focus on motion. focus on altering the loads applied to the foot (TST, PMP)
2. compensation of structural alignment issues may cause increased stress on soft tissue in gait (Root, TST)
3. address out of plane sagittal influences that could create functional hallux limitus (SPF, root, TST)
4. ensure mm balance between antag/agonist (TST, rotational equilibrium, PMP)

Question 10

outline the compensation mechanisms for sagittal plane blockage

Answer 10

• MTJ can’t lock –> arch compression
• early heel lift (apropulsive gait)
• inefficient windlass mechanism
• potential lateral columb loading (i.e. supinated foot) to avoid loading foot
• increased transverse plane motion (abd/add) during propulsion