Normal Motion of Foot and Leg in Gait Flashcards
Stance phase is divided into 3 periods
Contact Period
Midstance Period
Propulsive Period
Contact Period
Heel strike to foot flat
Midstance Period
Foot flat to heel off
Propulsive Period
Heel off to Toe off
Contact Period Action
HS, calcaneus contacts ground in slightly supinated position
STJ pronating
Lower leg internally rotating
Calcaneus everting, causing midtarsal joint axes to become parallel, allowing relatively free motion at joint
Allows for adaptation of foot to uneven terrain
Muscle Action in Contact Period
Tibialis anterior responsible for decelerating plantarflexion at heel strike, also supinates forefoot so lateral side of forefoot makes contact, eventually overcome by GRF
Leg internally rotated causing STJ pronation
Tibialis posterior decelerates pronation of STJ, also responsible to for decelerating anterior momentum of tibia
Midstance Period
Leg rotates externally
Closed chain supination
Talus abducts and dorsiflexes
Calcaneus inverting, causing midtarsal joint axes to become divergent, which allows less free motion in the foot
Foot is becomes more rigid lever to accept weight in preparation for the propulsive phase
Shortly before heel lift, with midtarsal axes divergent, GRF acts on midstarsal joints locking forefoot against rear foot, which is necessary for normal propulsion
Muscle Action in Midstance Period
Tibialis Posterior, soleus, long digit flexors start STJ supination and external rotation, also decelerate forward momentum of tibia
Gastrocnemius activity increases external rotation of femur at origin
Late midstance, STJ moves through its neutral position into supinated position before heel lift
Peroneus longus, brevis resist supinatory force of the calf muscle, control rate and extent of supination
Muscle Action in Midstance Period 2
Soleus plantarflexes ankle, slightly supinating STJ, stabilizes lateral side of foot against ground, stabilizes cuboid so that it can act as pulley for Peroneus Longus
Peroneus Longus turns around cuboid to insert in base of the 1st ray, pulls laterally against midfoot bones while tibialis posterior pulls medially, Peroneus brevis contributes to ensure balance between the two
Results in posterior force stabilizing mid foot against rear foot
Intrinsics stabilize metatarsus during last half of midstance, they are more effective when foot is supinated
Weakness of tibialis posterior or spasm of peroneus brevis results in unopposed abduction force on forefoot
Muscle Action in Midstance Period 3, Stabilizing the 1st ray
With foot supinated, Peroneus Longus pulls in a plantar posterior and lateral direction, using the cuboid as a pulley
Peroneus force is directed at stabilizing first ray against the vertical ground reaction force
Stable first ray necessary before hallux can be stabilized to perform normal weight receptive function during propulsion
When foot is pronated, peroneus longus pulls more laterally than plantarward, cannot effectively stabilize 1st ray against ground reaction force
Propulsive Period
STJ supinates
Leg externally rotates
Calcaneus inverts until just before toe off
Foot is very rigid lever designed for propulsion rather than accomodation
Propulsive period muscle activity 1
During early stage of propulsive period, all calf muscles contribute to ankle joint plantarflexion
During last half of the propulsive period, only long digital flexors appear to be responsible for ankle plantarflexion
Lubricals and digit extensors turn lesser toes into “rigid beams”
Propulsive period muscle activity, maintenance of transvere arch
Forefoot stabilized transversely by transverse pedis muscle
Dependent on stabile origin, hallux
Contract so that metatarsal heads do not splay
If foot abnormally pronated, hallux stability diminished, effectiveness of transverse pedis muscle decreased
Factors that influence propulsive period stability of the hallux
Peroneus longus stabilizes the base of the 1st ray
Abductor Hallucis (along with adductor hallucis, flexor hallicis longus and brevis) strong plantarflexor of the 1st ray, stabilizes 1st met head against underlying sesamoids
Tibial and fibular sesamoids serve as pulleys for muscles which stabilize the hallux against the ground during propulsion (as patella does for quadriceps)
Swing Phase
Begins after Toe off
Foot pronates from supinated position at TO to a pronated position in midswing
Foot supinates out of pronated position into slightly supinated position at the end of swing phase
