What are foot forces?
Force applied to the ground by the foot
What are ground reaction forces (GRF)?
Forces applied to the foot by the ground
T/F Foot forces and GRF are equal in magnitude in the same direction
False equal in magnitude but in opposite directions
What is the center of pressure?
Point where the GRF acts on the foot
EX: is GRF travels posterior to ankle it will create what type of external torque? What internal torque must we counter with?
External = plantar flexion Internal = dorsi
How can internal torque be created?
o Primarily created by muscle activation (lig, joint capsule, tendons will also assist)
o Passive internal structures
When there is concentric muscle activation, what is occurring at joint?
What are 2 goals of concentric muscle activation?
internal torque is moving the joint in the direction of the muscle’s action
Goal:
o Stability
o Produce movement of a segment
When there is eccentric muscle activation, what is occurring at joint?
What are 2 goals of eccentric muscle activation?
internal torque is moving the joint in the direction opposite of the muscle’s action
Goals:
o Shock absorption
o Decelerating a limb segment
When a muscle is peaking during gait, what does that mean?
exhibit the most electrical activity or greatest contraction
When a patient has muscular dysfunction, GRFV will not change, but what will?
Patient’s ability to counter it - can lead to altered gait patterns and compensations
Goal of muscle activation at IC in sagittal plane?
stop leg from buckling and prepare for weight acceptance
Describe what is happening at hip/knee/ankle muscle activation in sagittal plane at the IC phase of gait?
- Hip - ALL Hip extensors contract concentrically to prepare for LR
- Knee
o Eccentric hamstring contraction to counteract extension torque
o Knee extensors transition from concentric to eccentric contraction in preparation for loading response - Ankle (plantar flexor moment) - Pretibials (tib ant, long toe extensors) contract concentrically
What critical events happening during LR phase?
- Hip stability
- controlled knee flexion for shock absorption
- ankle plantar flexion
Describe what is happening at hip/knee/ankle muscle activation in sagittal plane at the LR phase of gait?
- Hip - Concentric contraction of hip extensors (Gmax, Adductor Magnus, TFL, GMed peak)
- Knee - Eccentric contraction (shock absorption) of knee extensors (Quadriceps activity peaks)
- Ankle - Eccentric contraction (slow down) of ankle dorsiflexors (Tibialis anterior peaks)
o Transition to eccentric contraction of ankle plantarflexors in late LR
What critical event is happening during MSt phase?
controlled tibial advancement
Describe what is happening at hip/knee/ankle muscle activation in sagittal plane at the MSt phase of gait?
- Hip - No hip muscular activity required in sagittal plane
- Knee - Quads eccentric to no activity
- Ankle - Eccentric contraction of gastroc/soleus
What critical event is happening during TSt phase?
controlled ankle dorsiflexion with heal rise
Describe what is happening at hip/knee/ankle muscle activation in sagittal plane at the TSt phase of gait?
- Hip - Minimal activity in sagittal plane
- Knee - No quad or HS activity
(Tibial position maintained by gastroc) - Ankle - Concentric contraction of ankle plantarflexors to prevent tibial collapse with heel rise
(Gastroc/soleus activity peaks)
What critical events occur with PSw phase?
- passive knee flexion to about 40
- ankle plantar flexion
- mtp extension of about 60
Describe what is happening at hip/knee/ankle muscle activation in sagittal plane at the PSw phase of gait?
- Hip - Concentric contraction of hip flexors (Adductor longus peaks)
- Knee - Knee flexion is mainly passive (Slight concentric contraction of knee flexors and eccentric rectus (help thigh moving forward))
- Ankle - Ankle plantarflexor activity ceases in early preswing and passive tension contributes to ankle moving into plantar flexion
o Ankle dorsiflexor concentric contraction initiated at the end of PSw
What critical events occur with ISw phase?
- hip flexion to about 15
2. full knee flexion to 60 so we can clear foot
T/F there is no ground reaction forces to match in ISw phase
True, because limb is in air
Describe what is happening at hip/knee/ankle muscle activation in sagittal plane at the ISw phase of gait?
- Hip - Continued concentric contraction of hip flexors
(Iliacus peaks) - Knee - Concentric contraction of knee flexors
(Biceps femoris (SH), sartorius, gracilis peak)
o Flexion continues to be aided by flexion at the hip - Ankle - Concentric contraction of tib anterior (Toe extensor activity peaks)
What critical events occur at MSw phase?
- further hip flexion
2. ankle dorsi to 0 to clear foot
Describe what is happening at hip/knee/ankle muscle activation in sagittal plane at the MSw phase of gait?
- Hip
o Continued concentric contraction of hip flexors
o Initiation of eccentric hip extensors (HS) (slow down limb in OKC) to control hip flexion - Knee
o Knee extension created by momentum
o Knee flexors contract eccentrically at the end of MSw to control extension - Ankle
o Continued concentric contraction of dorsiflexors
What critical event occurs at TSw?
Knee ext to neutral
Describe what is happening at hip/knee/ankle muscle activation in sagittal plane at the TSw phase of gait?
- Hip
o Concentric contraction of hip extensors - Knee
o Concentric contraction of knee extensors to insure full extension
o (Peak hamstring eccentric contraction to decelerate thigh) - Ankle
o Continued concentric contraction of dorsiflexors
At what phase does GMed peak?
Concentric contraction of hip extensors during LR
At what phase do quads peak?
Eccentric contraction (shock absorption) of knee extensors during LR
At what phase do Tib anterior peak?
Eccentric contraction (slow down) ankle dorsiflexion during LR
At what phase do the gastroc/solesu peak?
Concentric contraction of ankle plantarflexors to prevent tibial collapse with heel rise during TSt
At what phase does the adductor longus peak?
Concentric contraction of hip flexors during PSw
At what phase does the iliacus peak?
Continued concentric contraction of hip flexors during ISw
At what phase do the toe extensors peak?
Concentric contraction of tib anterior during ISw
At what phase do the hamstrings peak?
eccentric contraction to decelerate thigh during TSw
T/F Knee has no movement in frontal plane
True
Muscle activation in frontal plane during LR for hip/ankle?
- Hip
Hip abductors contracting eccentrically
GMed & Adductor Magnus peak (stays active throughout entire stance face = eccentric to concentric) - Ankle
Inverters contracting eccentrically
Muscle activation in frontal plane during MSt for hip/ankle?
- Hip
Hip abductors contracting eccentrically then concentrically - Ankle
Inverters contracting eccentrically
Muscle activation in frontal plane during TSt and PSw for hip/ankle?
- Hip
Hip abductors contracting concentrically (level pelvis, turn back on to get ready for weight acceptance) - Ankle
Inverters contracting concentrically
Muscle activation in frontal plane during ISw, MSw, and TSw for hip/ankle?
- Hip - Hip adductor contract concentrically (help advance leg)
- Ankle - Evertors contracting concentrically
What are the key roles of the ankle dorsiflexors during gate?
Eccentric activation to control plantar flexion of the ankle at IC until foot flat
What are the key roles of the ankle plantar flexors during gate?
- Eccentric contraction moving into MSt to control tibial advancement
- Concentric contraction at TSt assists with forward propulsion
What are the key roles of the ankle invertors (tib posterior) during gate?
- Eccentrically contracts to control pronation until MSt
2. Concentrically contracts to supinate the foot for push-off in TSt/PSw
What are the key roles of the ankle evertors during gate?
Also active as co-contraction to counter strong inversion effect occurring during LR/MSt
What are the key roles of the knee extensors during gate?
- Eccentrically control knee flexion in LR (shock absorbers)
- Concentrically to extend the knee and support body in MSt
What are the key roles of the knee flexors during gate?
- Decelerate knee extension in preparation for placement of the foot on the ground (eccentrically)
What are the key roles of hip extensors during gait?
- Activated in TSw prior to IC to initiate hip extension and prepare LE for weight acceptance at the beginning of stance
What are the key roles of hip flexors during gait?
- Advance lower extremity forward during ISw
2. Concentrically lift lower extremity to allow for toe clearance during swing
What are the key roles of hip abductors during gait?
- Control the slight lowering of the contralateral pelvis on the side of the swing limb then provide pelvic stability in stance
What are the key roles of hip adductors during gait?
- Assist with initiation of hip flexion after toe off
Trendelenburg Gait: Phase? Plane? Observation? Causes? Result?
- Phase: LR-PSw
- Plane: Frontal
- Observation: Excessive downward drop of the contralateral pelvis during stance
- Causes: GMed weakness (mild)
- Result: functionally longer swing limb, decreased efficiency, possible decreased stance time
Compensated Trendelenburg: Phase? Plane? Observation? Causes? Result?
- Phase: LR-PSw
- Plane: Frontal
- Observation: trunk lean toward over the stance limb, level pelvis
- Causes: GMed weakness (moderate - severe)
- Result: compensates by not allowing the contralateral pelvis to drop during stance by reducing demand on GMed
Foot Slap: Phase? Plane? Observation? Causes? Result?
- Phase: IC-LR
- Plane: Sagittal
- Observation: PF torque goes unchecked by anterior tib
- Causes: Tib Ant weakness (peroneal n. palsy, or peripheral neuropathy)
- Result: Rapid PF after heel contact, can be audible. Usually can clear foot during swing
Knee Extension Thrust: Phase? Plane? Observation? Causes? Result?
- Phase: IC
- Plane: Sagittal
- Observation: Knee snapping back into extension early in stance phase
- Causes: Quad spasticity from UMN lesion
- Result: Rapid and often excessive knee extension during LR, can occur w/cause knee hyperextension over time