Gait & basic foot kinematics
Gait cycle
- stance phase (62%)
- 3 components
- heel strike, foot flat & toe off
- swing phase (38%)
- double legged support (12%) followed by an intermediate phase (38%) then another period of double legged support
- In running there is no period of double legged support; indeed there is a float phase when neither foot is in contact with the ground
- During Gait
- centre of mass (anterior to S2) moves 5cm laterally
Shock absorption
- Ground reaction forces during walking reach 1.5 times body weight. During running they are 3 times body weight
- Shock absorption by the hindfoot, ankle & motors acting across them is very important to reduce stresses across the leg & back
- Factors involved are
- Static structures
- Heel pad
- Dynamic structures
- Eccentric contractions of muscles e.g. tibialis anterior
- Controlled descent of the forefoot after heel strike is the most important function of tibialis anterior
- Absence of tib anterior function results in foot slap
- Tibialis posterior
- Contraction results in controlled hindfoot eversion
- Gastrocsoleus
- Controls forward motion of the tibia relative to the foot
- Change in vectors – the axial load of impact is dissipated by partly converting it to a rotatory load, as the talus & tibia internally rotate on heel strike
Accommodation to surface irregularities
- Achieved by the freedom of movement in the subtalar & transverse tarsal joints
Push off
- At push off the flexible foot converts to a rigid one, to allow propulsion
- How does this occur?
- At foot strike the tibia internally rotates, the calcaneus assumes a valgus posture & the subtalar joint everts
- As the pelvis rotates towards the stance foot the tibia externally rotates
- This causes external rotation of the talus, in particular its head
- This results in the orientation of the axes of the talonavicular joints & the calcaneocuboid joints changing from parallel to divergent
- divergent axes lock the transverse tarsal joint & make the foot rigid
- calcaneus assumes a varus posture & the subtalar joint inverts
- Other factors
- Tightening of the plantar fascia via the windlass effect: the fascia arises from the medial side of the calcaneus & as it tightens it pulls the calcaneus into varus
- Contraction of Tibialis Posterior which holds the navicular medially on the talar head
- Contraction of the peroneus longus which plantar flexes the first ray
Columns of the foot
- medial column consists of the medial navicular, medial cuneiform & 1st MT
- middle column consists of the lateral navicular, intermediate & lateral cuneiforms & the 2nd & 3rd MT
- lateral column consists of the cuboid & the 4th & 5th MT
Webpage Last Modified:
18 February, 2010