Contact Period

Adaptation to surface terrain

• [how is this possible] 

• Pronation of the subtalar joint allows a laxness in the forefoot 

contact period

Ankle Joint Plantarflexion

• Ankle joint plantarflexes in the sagittal plane from [...] to [...] in the contact period
  

  • Why? Because plantarflexion allows the mets to come in contact with the ground in order to load the forefoot

• Between [...] and [...], the ankle dorsiflexes

• As the foot plantarflexes at the ankle joint, it will also adduct
  

  • Due to the anatomy of the trochlea of the talus 

• heel strike to forefoot contact

• forefoot contact and actual forefoot loading

Ankle Joint Plantarflexion

• Ankle joint plantarflexes in the sagittal plane from heel strike to forefoot contact in the contact period
  

  • Why? [...]

• Between forefoot contact and actual forefoot loading, the ankle dorsiflexes

• As the foot plantarflexes at the ankle joint, it will also adduct
  

  • Due to the anatomy of the trochlea of the talus 

Because plantarflexion allows the mets to come in contact with the ground in order to load the forefoot

Ankle Joint Plantarflexion

• Ankle joint plantarflexes in the sagittal plane from heel strike to forefoot contact in the contact period
  

  • Why? Because plantarflexion allows the mets to come in contact with the ground in order to load the forefoot

• Between forefoot contact and actual forefoot loading, the ankle dorsiflexes

• As the foot plantarflexes at the ankle joint, it will also [...]
  

  • Due to [...] 

• adduct

• the anatomy of the trochlea of the talus 

As we enter the contact period, center of mass is [...] 

By the end of the contact period, center of mass is [...]

• behind the foot 

• right above the foot

At heel strike

• Forefoot is [supinated or pronated] about the LMTJ axis due to contraction of the anterior tibialis muscle

• Forefoot is [supinated or pronated] about the OMTJ axis due to contraction of the Extensor Digitorum Longus and Peroneus Tertius muscles

• supinated

• pronated

• Anterior tibialis m. contracts during the swing face

• Remember, supination about the LMTJ means the forefoot is inverted relative to the rearfoot 

• Extensor Digitorum Longus and Peroneus Tertius muscles were pronating during the swing phase so that during heel strike, it is already pronated

At heel strike

• Forefoot is supinated about the LMTJ axis due to contraction of the [...] muscle

• Forefoot is pronated about the OMTJ axis due to contraction of the Extensor Digitorum Longus and Peroneus Tertius muscles 

anterior tibialis

• Anterior tibialis m. contracts during the swing face

• Remember, supination about the LMTJ means the forefoot is inverted relative to the rearfoot 

• Extensor Digitorum Longus and Peroneus Tertius muscles were pronating during the swing phase so that during heel strike, it is already pronated

At heel strike

• Forefoot is supinated about the LMTJ axis due to contraction of the anterior tibialis muscle

• Forefoot is pronated about the OMTJ axis due to contraction of the [...] and [...] muscles 

Extensor Digitorum Longus and Peroneus Tertius muscles 

• Anterior tibialis m. contracts during the swing face

• Remember, supination about the LMTJ means the forefoot is inverted relative to the rearfoot 

• Extensor Digitorum Longus and Peroneus Tertius muscles were pronating during the swing phase so that during heel strike, it is already pronated

• Before forefoot hits the ground, it is controlled by [...]

• After forefoot hits the ground, it is controlled by [...]

• muscle contraction

• GFR

Calcaneus is everting and directing more of the body weight medially so the medial column begins to [...] as compensation for calcaneal eversion 

dorsiflex

Normal compensation for calcaneal eversion is forefoot inversion (or supination around the LMTJ) 

Closed Kinetic Chain Pronation

• Calcaneus partial pronation
  

  • [...] is the only motion we see in the calcaneus

  • Calcaneus cannot abduct due to forefoot contact with the ground

  • Calcaneus cannot dorsiflex due to the lateral arch and stability of the lateral column 

Eversion

Closed Kinetic Chain Pronation

• Calcaneus partial pronation
  

  • Eversion is the only motion we see in the calcaneus

  • Calcaneus cannot abduct due to [...]

  • Calcaneus cannot dorsiflex due to [...]

• forefoot contact with the ground

• the lateral arch and stability of the lateral column 

Closed Kinetic Chain Pronation

• Talus partial supination  
  

  • Talus [...]

  • Talus [...]

  • Talus will not invert because talus will not invert unless the leg inverts and since the leg doesn’t invert during normal gait, the talus also will not invert 

• adduction

• plantarflexion

Closed Kinetic Chain Pronation

• Talus partial supination  
  

  • Talus adduction

  • Talus plantarflexion

  • Talus will not invert because [...]

talus will not invert unless the leg inverts and since the leg doesn’t invert during normal gait, the talus also will not invert 

Closed Kinetic Chain Pronation

• Whole story
  

  • [...] causes [...] due to the facets between the calcaneus and the talus

  • Then, [...] moves the talus a little bit off the calcaneus which allows [...] 

• Talus adduction causes calcaneus eversion

• calcaneus eversion

• talus plantarflexion 

Closed Kinetic Chain Pronation

• [What's different about it from the open kinetic chain pronation?] 

Difference from open kinetic chain pronation, which just involves the foot is that this involves the particular joints, because contact with the ground introduces forces that affect different joints differently 

Contact Period

• Duration
  

  • Begins at [...]

  • Ends with [...] of the observed foot & [...] of the opposite foot

  • 27% of the stance phase of gait 

• heel contact

• forefoot loading

• toe off

Contact Period

• Duration
  

  • Begins at heel contact

  • Ends with forefoot loading of the observed foot & toe off of the opposite foot

  • [...]% of the stance phase of gait 

27%

Detailed response why the foot is able to be a mobile adapter during the contact period. 

• [...] 

• [...] 

• [...] 

• STJ pronation causes calcaneus eversion 

• Forefoot compensates for calcaneus eversion by supinating around the LMTJ 

• Since we see supination about the LMTJ and pronation about the OMTJ, this means the midtarsal joint is partially unlocked and the foot can be a mobile adaptor 

Fully locked midtarsal joint is maximally pronated about both axis

• Double limb support during [...] period

• Single limb support is only seen during the [...] period 

• contact

• midstance

Hip Extension

• During the start of contact period:
  

  • Hip is [flexed or extended] due to [...]

• During the contact phase:
  

  • The flexed hip begins to extend

• Internal rotation of the hip by:
  

  • Pelvis and thigh internally rotate but the thigh rotates faster and further than the pelvis 

• flexed

• bringing the leg from behind the body to in front of the body

Hip Extension

• During the start of contact period:
  

  • Hip is flexed due to bringing the leg from behind the body to in front of the body

• During the contact phase:
  

  • [...]

• Internal rotation of the hip by:
  

  • Pelvis and thigh internally rotate but the thigh rotates faster and further than the pelvis 

• The flexed hip begins to extend

In the normal foot, pronation of the STJ should only be in the [...] period

contact

Internal Leg Rotation

• Internal rotation of the leg causes subtalar joint pronation

• STJ as a torque converter
  

  • Subtalar joint converts transverse plane motion to frontal plane motion 

• Foot is able to dissipate torque on the frontal plane because [...]
  

  • Less shear force vectors to resist frontal plane motion

  • Joints are designed to handle frontal plane motion better

more motion is available in the foot in the frontal plane overall

Internal Leg Rotation

• Internal rotation of the leg causes subtalar joint pronation

• STJ as a torque converter
  

  • Subtalar joint converts transverse plane motion to frontal plane motion 

• Foot is able to dissipate torque on the frontal plane because more motion is available in the foot in the frontal plane overall
  

  • [two reasons why]

  • [...]

• Less shear force vectors to resist frontal plane motion

• Joints are designed to handle frontal plane motion better

Knee Flexion

• During the swing phase, the knee [...]

• During the contact period, the knee [...]

• is undergoing extension

• goes from an extended position to knee flexion

• Knee flexion is the primary way to dissipate shock from heel contact

• Internal rotation at the knee joint

  • Due to tibia internally rotating faster and further than the thigh 

Loading of the Forefoot

• At heel strike, then, the midtarsal joint is [fully locked or partially locked?]

• partially locked

Fully locked midtarsal joint is maximally pronated about both axis

Partially locked due to supination around the LMTJ preventing maximal pronation 

Loading of the Forefoot

• Pronated around the OMTJ due to [...] 

• head of 5th Metatarsal contacting the ground first 

Fully locked midtarsal joint is maximally pronated about both axis

Partially locked due to supination around the LMTJ preventing maximal pronation 

Loading of the Forefoot

• Smooth loading of forefoot from lateral to medial allowed by:
  

  • [...]

  • [...] 

• Ground reactive forces (pushing up on the 5th met first)

• Relaxation of the Anterior Tibialis m. 

Fully locked midtarsal joint is maximally pronated about both axis

Partially locked due to supination around the LMTJ preventing maximal pronation 

Peaking Vertical Forces

• First peak of vertical GRF is at [...]

• Peak in posterior shear force at [...]

• Decrease in vertical forces as the forefoot loads and evenly distributes the forces through the foot 

• the end of the contact period

• the end of the contact period

Peaking Vertical Forces

• First peak of vertical GRF is at the end of the contact period

• Peak in posterior shear force at the end of the contact period

• Decrease in vertical forces as [...] 

• the forefoot loads and evenly distributes the forces through the foot 

contact period

Shock absorption

• [pronation or supination] of the STJ turns the foot into a mobile adapter to dissipate shock

• STJ functions as a torque converter
  

  • Converts transverse plane rotation of the leg to frontal plane calcaneal motion

  • Possible due to its deviations

Pronation

Deviations

• 42 degrees deviated from the transverse plane

• 48 degrees deviated from the frontal plane
  

  • SO, the angle is almost at 45 degrees which indicates as much frontal plane motion as transverse plane motion so it can convert motion from the transverse plane to the frontal plane 

Shock absorption

• Pronation of the STJ turns the foot into a mobile adapter to dissipate shock

• STJ functions as a torque converter
  

  • Converts [...] to [...]

  • Possible due to its [...]

• transverse plane rotation of the leg to frontal plane calcaneal motion

• deviations

Deviations

• 42 degrees deviated from the transverse plane

• 48 degrees deviated from the frontal plane
  

  • SO, the angle is almost at 45 degrees which indicates as much frontal plane motion as transverse plane motion so it can convert motion from the transverse plane to the frontal plane 

Triplane motion of closed kinetic chain at the STJ

• [...] of the [...]

• [...] of the [...]

• [...] of the [...]

Triplane motion of open kinetic chain of the foot (pronation)

• Abduction of the foot

• Eversion of the foot

• Dorsiflexion of the foot 

• Adduction of the talus

• Eversion of the calcaneus

• Plantarflexion of the talus

Triplane motion of closed kinetic chain at the STJ

• Adduction of the talus

• Eversion of the calcaneus

• Plantarflexion of the talus

Triplane motion of open kinetic chain of the foot (pronation)

• [...] of the [...]

• [...] of the [...]

• [...] of the [...] 

• Abduction of the foot

• Eversion of the foot

• Dorsiflexion of the foot 

We need motion that will provide linear acceleration (to move the body forward). It is done so by:

1. [...]

2. [...]

3. [...] 

1. During contact period, the opposite foot is in its propulsive period

2. Transverse motions: rotation of the foot, tibia, femur, pelvis and upper trunk

3. Sagittal motions: shift of center of gravity anterior to the center of foot support 

Sagittal motions:

• as we enter the contact period, the leg is in front of the body so our center of mass is behind the foot. By the end of contact period, center of mass moves forward until it is over the foot . 

[...]

• Idea that gait is like a fall forward that is controlled by muscle contraction so the body progresses forward 

Fall forward

[...] is the primary way to dissipate shock from heel contact 

Knee flexion