The Human Foot

The complicated anatomy of the foot is targeted at generating propulsive force for running and walking and at coping with the body weight. The ankle mortise holds the talus firmly and it sits at the top of the main long ways arch of the foot. The medial or longitudinal foot arch is the biggest one, this takes the standing, and moving loads of the body with the spring ligament absorbing and releasing some of the energy involved. The outside, lateral arch is much smaller as is the arch across the front of the foot between the fifth and first metatarsal heads.

The foot is a propulsion and support system for the body’s weight and without the arches it would be unable to undertake this role with the dynamism required. The energy generated by the acts of walking or running are absorbed and then released as the gait cycle is completed. On observing a person walking with painful and flat feet the gait is clearly clumsy and the feet inflexible platforms, unable to adapt to the changing surfaces and forces transmitted through the feet. Healthy arches are crucial to maintain comfort and mobility as we age.

The foot has two functions to perform: to cope with and distribute the weight of the body which is often multiplied by movement and to generate propulsive forces to push off in walking. The foot arches are partly maintained by the calf muscles previously mentioned in an article about the ankle, but also by the muscles controlling the toes. The long flexor muscles of the toes also start in the calf and run under the sole to the forefoot and toes, curling the toes or gripping the ground. The short flexor muscles, which start in the feet and again go to the toes, are known as the intrinsic muscles and work by pressing the toes down into the surface but without bending them.

When a person with a normally functioning foot takes a step the first contact with the ground is with the heel somewhat on the outside. As the step continues the lower leg rolls over the talus inside the ankle joint and the foot arches, the joints and ligaments, absorb the energies of weight bearing and movement. Moving forwards and inwards, the weight is borne finally by the metatarsal heads of the second and first toes, with the final push from the toe muscles.

Accessory movements, tiny involuntary movements which naturally occur within joints as they move but cannot be done independently, are present in the foot as they are in any bodily motion joint. Normal function of a joint depends at least partly on the presence of accessory movements and will suffer if they are lost or reduced. The foot has a large amount of small bones in very close relationship and constructed into complex anatomy such as the foot arches. Numerous accessory movements occur between the many joints.

As the body weight starts to be borne on the foot the arches begin to suffer a flattening effect which is countered by the calf and toe muscle strength and the ligamentous elasticity and tension. As the gait cycle approaches the push off point the arches are supported against the weight by the toes gripping the ground, the energetic ligament recoil and the muscular sling support provided by the calf muscles. As walking proceeds the arches heighten and lower in a cyclical movement during which the complex multiple joint complexes of the arches exhibit continual accessory movement between all the bones.

Each bone of the foot needs to have the ability of independent movement relative to the others, with weight causing the underneath of the joints to open as the upper surfaces close. The individual ability to accommodate to the surfaces which present themselves is vital, allowing the foot to adjust to the dynamic circumstances required. Losing some of the range of accessory movement makes the foot lose some of its dynamic flexibility as it changes into a more static body weight prop from the active organ of propulsion.

Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about physiotherapy, physiotherapy, physiotherapists in Solihull, back pain, orthopaedic conditions, neck pain and injury management. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.