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Foot & Ankle Biomechanics

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Topic updated on 07/24/14 11:22am
Ankle Biomechanics
  • Ankle joint
    • consists of 
      • tibial plafond
      • medial malleolus
      • lateral malleolus
      • talus
    • motion
      • main motion
        • plantar flexion
        • dorsiflexion
      • secondary motions
        • inversion/eversion
        • rotation
  • Distal tibiofibular joint
    • consists of
      • distal fibula
      • incisura fibularis
        • concave surface of distal lateral tibia
    • motion
      • fibular rotates within incisura during gait
      • mortise widens when ankle goes from plantar to dorsiflexion
      • syndesmosis screws limit external rotation
  • Joint reaction force 
    • ankle joint
      • 5 times body weight with walking on level surfaces
Hindfoot Biomechanics
  • Subtalar joint
    • consists of articulation between
      • talus
      • calcaneus
    • motion
      • inversion/eversion
      • plays no role in plantar and dorsiflexion
  • Transverse tarsal joint (Chopart joint)
    • consists of
      • talonavicular articulation
      • calcaneocuboid articulation
    • motion  
      • inversion of subtalar joint locks the transverse tarsal joint  
        • allows for a stable hindfoot/midfoot for toe-off
      • eversion of subtalar joint unlocks the transverse tarsal joint
        • allows for supple foot to accommodate ground just after heel strike
      • plantar aponeurosis is primary structure of load/force transfer between hindfoot and forefoot during stance 
Midfoot Biomechanics
  • Consists of
    • intercuneiform joints
    • naviculocuneiform joint
    • tarsalmetatarsal joints (lisfranc joints)
      • divided into three columns
        • medial column
          • first metatarsal
          • medial cuneiform
          • navicular
        • middle column
          • second and third metatarsals
          • middle cuneiform
          • lateral cuneiform
        • lateral column
          • forth and fifth metatarsals
          • cuboid
  • Motion
    • lateral column is the most mobile
      • allows for flexibility when walking on uneven ground
    • middle column is the least mobile
      • allows for rigidity during push-off
    • medial column carries most of load while standing
Forefoot Biomechanics
  • Consists of
    • metarsalphalangeal joints
    • proximal interphalangeal joints
    • distal interphalangeal joints
  • Joint reaction forces
    • second metatarsal experiences more stress during gait
      • most commonly metatarsal to have a stress fracture
The Gait Cycle
  • Overview
    • one gait cycle is measured from heel-strike to heel-strike
    • consists of
      • stance phase
        • period of time that the foot is on the ground
        • ~60% of one gait cycle is spent in stance
      • swing phase
        • period of time that the foot is off the ground moving forward
        • ~40% of one gait cycle is spent in swing
  • Phases of the gait cycle  
    • stance phase ("I Like My Tea Presweetened")  
      • initial contact (heel strike)
        • definition
          • occurs when foot contacts the ground
        • muscular contractions
          • hip extensors contract
          • quadriceps contract eccentrically
          • tibialis anterior contracts eccentrically
      • loading response (initial double limb support)
        • definition
          • occurs after initial contact until elevation of opposite limb
        • muscular contractions
          • ankle dorsiflexors (tibialis anterior) contract eccentrically to control plantar flexion moment
          • quads contracts to stabilize knee and counteract the flexion moment (about the knee)
      • mid-stance (single limb support)
        • definition
          • from elevation of opposite limb until both ankles are aligned in coronal plane
        • muscular contractions
          • hip extensors and quads undergo concentric contraction
      • terminal stance (single limb support)
        • definition
          • from when ankles are aligned to until the opposite to when heel strikes in contralateral limb
        • muscular contractions
          • toe flexors contract
      • pre-swing (second double limb support)
        • definition
          • from initial contact of opposite limb to just prior to elevation of ipsilateral limb
        • muscular contractions
          • hip flexors contract to propel advancing limb
    • swing phase ("In My Teapot")  
      • initial swing (toe off)
        • definition
          • from elevation of limb to point of maximal knee flexion
        • muscular contractions
          • hip flexors contract
      • mid-swing (foot clearance)
        • definition
          • following knee flexion to point where tibia is vertical
        • muscular contractions
          • ankle dorsiflexors contract to ensure foot clearance
      • terminal swing (tibia vertical)
        • definition
          • from point where tibia is vertical to just prior to initial contact
        • muscular contractions
          • hamstring muscles decelerate forward motion of thigh
  • Center of gravity (COG)
    • 5cm anterior to S2 vertebral body
    • displaced 5cm horizontally and 5cm vertically during adult male step
  • Determinants of gait
    • pelvic rotation
      • pelvis rotates 4 degrees medially (anteriorly) on swing side
        • lengthens the limb as it prepares to accept weight
    • pelvic tilt
      • pelvis drops 4 degrees on swing side
        • lowers COG at midstance
    • knee flexion in stance
      • early knee flexion (15 degrees) at heel strike 
        • lowers COG, decreasing energy expenditure
        • also absorbs shock of heel strike
    • foot mechanisms
      • ankle plantar flexion at heel strike and first part of stance
    • knee mechanisms
      • at midstance, the knee extends as the ankle plantar flexes and foot supinates
      • restores leg to original length
      • reduces fall of pelvis at opposite heel strike
    • lateral displacement of pelvis
      • pelvis shifts over stance limb 
        • COG must lie over base of support (stance limb)
 

 

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Qbank (7 Questions)

TAG
(OBQ12.118) Which of the following best describes the relationship of the subtalar and transverse tarsal joints during the phases of gait? Topic Review Topic

1. Eversion of the subtalar joint locks the transverse tarsal joint
2. Transverse tarsal (Chopart) joint axes are parallel during heel strike
3. The calcaneus is in inversion throughout stance phase
4. Tibialis anterior concentrically contracts during stance phase
5. During push-off the foot becomes flexible due to eversion of the calcaneus

PREFERRED RESPONSE ▶
TAG
(OBQ12.237) Which phase of gait is affected most in a patient with quadriceps atrophy? Topic Review Topic

1. Terminal swing
2. Preswing
3. Initial swing
4. Midstance
5. Midswing

PREFERRED RESPONSE ▶
TAG
(OBQ10.123) Which of the following descriptions of muscle activity during normal gait is correct? Topic Review Topic

1. Gastrocnemius-soleus contracts eccentrically during heel strike
2. Gastrocnemius-soleus contracts concentrically during heel strike
3. Gastrocnemius-soleus contracts concentrically during swing phase
4. Tibialis anterior contracts concentrically during toe-off
5. Tibialis anterior contracts eccentrically at heel strike

PREFERRED RESPONSE ▶
TAG
(OBQ07.58) Which of the following does NOT occur during the normal push-off stance of the gait cycle? Topic Review Topic

1. subtalar joint inversion
2. transverse tarsal joint locks
3. external rotation of the lower extremity
4. tightening of the plantar fascia
5. loosening of the spring ligament

PREFERRED RESPONSE ▶
TAG
(OBQ06.6) Which of the following structures is the primary site of force transfer between the hindfoot and forefoot during the stance phase of gait? Topic Review Topic

1. Plantar aponeurosis
2. Achilles tendon
3. Lisfranc ligament
4. Posterior tibial tendon
5. Anterior tibial tendon

PREFERRED RESPONSE ▶
TAG
(OBQ06.222) The primary antagonist of the anterior tibial tendon is innervated by which of the following nerves? Topic Review Topic

1. Superficial peroneal nerve
2. Deep peroneal nerve
3. Tibial nerve
4. Posterior tibial nerve
5. Sural nerve

PREFERRED RESPONSE ▶
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