The anatomy of the foot

How the foot moves
November 19, 2015

The foot is a masterpiece of engineering. It has 26 different bones held together by strong ligaments and small muscles. These form arches with astonishing load-bearing capabilities. To be able to assess the wide range of foot problems correctly and to understand complaints, which are frequently based on static problems, the fascinating world of the structure of the foot has to be explored a little.

Of all the parts of the human body, the foot was most greatly affected by man’s coming to walk on two legs in the course of evolution. Originally the foot was for climbing and had a supinated posture, i.e. turned outwards. This gradually changed into a standing foot, which means the sole slowly turned downwards or pronated. This climbing foot is preserved in the structure of the metatarsals. However, exactly this structure with the transverse and longitudinal arches became the most important weight-bearing part of the foot walking flat on the ground. The residual skilfulness of the foot is demonstrated by how people who have lost their arms can learn to paint, cook and phone using their feet. Due to wearing the wrong footwear in childhood, being overweight and many other reasons, the feet of people today are but “a caricature of the ideal foot”. (Hohmann)

Arches

The structure formed by the many bones held by tendons gives the foot great flexibility and creates spring arches able to bear weight and absorb shocks.

Muscles

The muscles of the leg itself are strong and cover the bones in many layers. Apart from movement, they play a role in holding up the arches, stretching the skin, and supporting the sole.

The strong muscles of the lower leg are attached to the foot. By stretching the leg, some of them (the extensors) extend the foot and toes upwards, from the sole towards the head. The muscles forming the calf (the flexors) bend the foot towards the sole and when standing raise the body. Some muscles only move the toes, while others the whole foot.

Blood vessels and nerves

The main nerve moving and supplying sensation to the foot, the posterior tibial nerve, enters the sole of the foot running behind the inside bump on the ankle.

Blood is supplied to the foot mainly by two arteries. The more important one runs right behind the main nerve and the other runs down the top of the foot. The main blood vessel and nerve are protected by the inside bump of the ankle and branch on the sole of the foot. The artery on the top of the foot divides in a similar way, reaching right to the tips of the toes.

The small but important tendon of the posterior tibial muscle runs under the bump on the inside of the ankle and supports the longitudinal arch.

The large anterior tibial muscle comes from the shin and is attached to the inner side of the foot. When it contracts, the foot is raised from the ground.

The Achilles tendon is the common tendon for the calf muscles. It is attached to the heel at the back and plays a role in moving the foot. When it is flexed, the heel is raised, which is the most important phase of walking.

Extensor tendons run along the top of the foot to the toes. The extensor muscles of the toes are on the shin and work together with the anterior tibial muscle. Thus the toes are straightened by the muscles of the lower leg, while they are flexed by the foot’s own muscles.