Traditional Approach to the Gait Cycle
The gait cycle can be divided into two of phases – stance phase (makes up about 60% of cycle during normal walking speed) and swing phase (40%). Stance phase as a number of periods (varies depending on author) – descriptions include heel contact, forefoot contact, midstance, propulsion, heel off.
Another approach is to divide the stance phase into weight acceptance, single limb support and double limb support – it is only during single limb support when the contralateral limb is being advanced does forward progression occur.
Function of the foot: 1) Base of support
2) Shock absorber
3) Mobile adaptor
4) Rigid lever
• During this period foot adapts to terrain and absorbs shock
• Considered to consist of the first 10% of the stance phase – from heel contact to forefoot contact
• At contact hip is flexed (usually about 30 degrees), knee is extended, ankle is 90 degrees to the leg, subtalar joint is slightly supinated, midtarsal joint is supinated, and first ray is dorsiflexed
• As heel strikes leg is internally rotating foot will momentarily abduct until friction stops the movement and initiates subtalar joint pronation
• After initial contact the knee flexes, the ankle rapidly plantarflexes and the subtalar joint pronates
• Lateral side of forefoot contacts the ground first due to supinated MTJ – contact period ends when medial side of forefoot contacts ground.
• Prior to heel strike, the anterior tibial (AT) and extensor hallucis longus (EHL) muscle contract to decelerate ankle joint plantarflexion. AT dorsiflexes first ray plantarflexes hallux hallux becomes stable insertion for function of EHL
• At heel strike the tibialis posterior (TP) fires to decelerate STJ pronation and internal leg rotation.
• After forefoot contact, soleus fires to assist in STJ pronation deceleration and internal leg rotation. Soleus has a significant lever arm to STJ axis.
• During last half of contact, flexor digitorum contracts to assist TP and soleus. At end of contact flexor hallucis longus contracts to assist.
• Body weight moves over stationary foot – the foot is assumed to move from the ‘shock absorbing’ function during contact to the ‘rigid lever’ function during propulsion.
• Considered to consist of 10% to 30% of the gait cycle – from forefoot contact to heel off
• The knee and hip start to extend; subtalar joint pronation should have stopped and resupination begun. The leg starts to externally rotate
• Controversy exist about the position of the foot at the midstance period – Root et al (1977) believe the subtalar joint should be in its neutral position, but McPoil and Cornwall (1996) showed the mean of an asymptomatic population it is about 4 degrees everted.
• The muscles that decelerated subtalar joint pronation and internal leg rotation now supinate the STJ and externally rotate the leg.
• As the soleus supinates the STJ firmly hold cuboid on ground efficient pulley for peroneus longus so it can stabilise the first ray on the ground
• Tibialis posterior exerts a posterior medial force on tarsus and peroneus longus exerts a posterior lateral force on tarsus stabilises tarsus. Peroneus brevis resists the stronger adductory force of TP
• After these muscles have stabilised the tarsus, the intrinsic muscles then have stable attachments to contract to stabilise the metatarsus and digits before they accept body weight (theory of proximal stability)
• Foot becomes a more ‘rigid lever’ for efficient propulsion
• Considered to consist of 30% to 60% of the gait cycle – from heel off to toe off
• The knee flexes and the ankle plantarflexes
• The subtalar joint supinates; first ray plantarflexes; first MPJ dorsiflexes; windlass mechanism raises medial longitudinal arch – all this occurs as contralateral leg is in swing and the opposite hip is advancing forward external rotation of ipsilateral limb
• As the heel comes of the ground body weight is transferred to he medial side of the forefoot
• Heel lift is due to forward momentum of the body, deceleration of the tibia and active knee flexion
• As foot supinates the plantarflexor muscles of the first ray keep it firmly in contact with the sesamoids. The flexor hallucis muscles and the abductor and adductor muscles of the hallux firmly stabilise the hallux on the ground so it can receive weight and the first metatarsal can rotate and plantarflex about it
• Once hallux is stable transverse head of adductor hallucis (transverse pedis) muscle can contract to stabilise the lessor metatarsals in the transverse plane (theory of proximal stability)
• Lessor digits are stabilised into ‘rigid beams’ by extensor expansions extensor stability is by the long and short extensors and lumbrical muscles – long and short plantarflexes stabilise the toes on the ground. Transverse plane stability is achieved by the interosseous muscles.
• As weight comes of heel, soleus can no longer keep cuboid stable on ground peroneus longus can now off load the lateral side of the foot to transfer weight to the hallux for propulsion and subsequently to the other foot.
• Considered to consist of 60% to 100% of the gait cycle
• The hip continues to flex; the knee extends from a flexed position; ankle dorsiflexes; subtalar joint is slightly pronated at toe off
• Immediately after toe off, tibialis anterior and EHL contract to dorsiflex the foot to aid in ground clearance
• Little or no muscle activity during midstance
• Just prior to heel strike tibialis anterior and then EHL contract in preparation for decelerating plantarflexion.