Gait Test 1 Flashcards
Joint Reaction Force
2 bones compressed
Equal & opposite to ground reaction force in loading
Center of Pressure
Origin of ground reaction force (location of average weight bearing force)
- Commonly used to indicate postural stability
COP Excursion
Measure of balance
Trace of center of pressure as someone stands on force plate
Equations for:
Force
Pressure
Torque
F = mass*accel P = F*Area T = Force * moment arm
Support Moment
Sum of sagittal plane moments at ankle, knee, and hip
Total external torque demand on LE
Force required to support body in a certain position
Biomechanical Influence of backward trunk lean
- Hip flexion torque down (less glut max/hamstrings)
- Knee flexion torque up (more quads), more loading at knee
- Ankle PF torque up (more DF action)
4 functions of locomotor unit during gait that are needed to walk normally
- Shock absorption
- Stance stability
- Forward progression
- Energy conservation
Shock Absorption achieved by 2 things…
Passive - bone & cartilage
Active - eccentric muscle contractions absorb energy
(primarily eccentric quads)
Heel Rocker - 3 functions
Loading response, Due to normal heel strike
- Drives foot to floor
- Propels tibia forward, creates forward momentum
- Facilitates knee flexion
Ankle rocker
Midstance
Tibia forward –> COM translates over BOS
Forefoot rocker
Pivots on metatarsal heads, late stance
Lets COM progress beyond BOS
Center of mass oscillation during gait cycle
COM oscillates 4 cm medial/lateral and 2 cm up/down
Highest in midstance, lowest in double limb support
M/L shift over stance limb during single limb support
Locked position of midtarsal joints
Supination
supinated foot = rigid, pronated foot flexible
Purpose of pronation in loading response/midstance (3)
- Unlocks MT joints, turning foot into mobile adaptor –> shock absorption
- More contact with floor –> stability
- Facilitates tibia IR –> unlocks knee allowing 20º flexion
Purpose of supination in midstance/terminal stance (2)
Locks MT joints turning foot into rigid lever –> facilitates forefoot rocker
Dynamic control of foot pronation in loading response (4)
Eccentric inverters decelerate pronation of foot. Foot will continue to flatten if weakness
- Tib Post
- Tib Ant
- Flexor Hallucis Longus
- Flexor Digitorum longus
Dynamic control of supination in mid/terminal stance (3)
Concentric invertors 1. Tib post 2. Flexor hallucis longus 3. Flexor digitorum longus Not tib ant. because it also does DF
Influence of wide heel shoes on rearfoot mechanics
Shoes with wide lateral heel increase pronation torque because it moves the contact point laterally
Influence of flared heel on heel rocker mechanics
Increases PF torque
Increased demand on dorsiflexors –> potential cause of shin splints, tib ant overuse
Screw Home Mechanism
Due to curvature of condyles
In open chain NWB:
Tibia IR a few degrees before flexion, tibia ER a few degrees to lock into extension