The foot has a complex anatomy designed to bear the weight of the body and to propel the body forward in walking and running. The talus or ankle bone sits in the ankle mortise and is the top link of the main longitudinal arch of the foot. The longitudinal or medial arch is the largest and is on the inside of the foot, absorbing the loads in standing postures and aided in its elastic recoil by the spring ligament. The outside of the foot has a smaller arch known as the lateral arch and the front of the foot has a transverse (across) arch between the first and fifth 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 is designed to fulfil two main actions: to accept the forces generated in locomotion and generate propulsive forces to effect gait and to manage the forces involved in movement of the body weight which are often greatly increased by motion. Some of the calf muscles, as mentioned in an ankle article recently, function to keep the arches of the feet working but the long flexor muscles of the toes do this also. Originating from the calf and running underneath the foot to insert into the toes, these muscles bend the toes and work by gripping the ground for stability and movement. The shorter intrinsic muscles, originating in the feet and inserting in the toes, bend the toes whilst keeping them straight.

If the foot hits the ground in a person with a highly functional foot the heel will contact the surface first and slightly on the lateral side. The foot rolls forward as the talus rocks inside the ankle mortise and weight begins to be taken by the arches with the joints and ligaments absorbing the stresses. The weight transfers gradually over to the inside and through the first and second metatarsal heads until the foot pushes off partly with the power of the toes muscles.

Each moving joint in our body has a degree of accessory movements in it, which are limited and subtle internal movements between joint surfaces which cannot be exhibited in isolation. A normal joint depends to some degree on the accessory movements present within the joint and if these are lost or reduced the joint’s function is compromised. A high number of intricately designed foot bones are packed into a small area, creating the arches, and all these bones have highly functional accessory movements between them.

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 is the Superintendent of Physiotherapy at an NHS hospital in the South-West of the UK. He writes articles about back pain, neck pain, and injury management. If you are looking for Winchester physiotherapy visit his website.

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