The foot is the foundation on which we stand. If there are problems with your foot than you will have problems trying to take part in any sport.
A good foot is essential!
This post is the first in a series of three which is designed to give you a basic understanding of what lies under the skin of your foot and ankle and how it all works together to get you out there walking and running.
So, by the end of this article you will understand
The basic structure of the foot
How your foot functions
How to recognise your foot-type
If you look closely at the structure of the foot you will see that it is built out of a series of arches of bone.
Figure 1 shows the long arch in the inside of your left foot. You can clearly see that this is quite a high arch.
Figure 2 shows the long arch on the outside of your left foot. You can see that this arch is lower than the inside one.
In addition to the lengthways arches in the foot there are also an arch which runs across the foot from side to side. To see this arch you have to imagine taking a chain saw to the foot and looking back at the cut foot end.
This transverse arch is best seen across the mid foot at Cut A but it is also present at the base of the toes (Cut B). These arches are not fixed structures they are flexible which allow the foot to adapt to uneven ground.
Your foot is made up of a collection of 26 major bones – there are a couple of tiny bones which can be included taking it up to 27 or 28 depending on what you read, but the main bones are what I am considering here. I am not going to name all the bones in this fundamental article but give you a feel for how the bones fit together and their function.
The heel bone (Calcaneus) is the largest bone in the foot and in walking it hits the ground first.
It has a pad of fat in the skin under the heel to help absorb some of the shock.
The bone that sits on top of the Calcaneus is the Talus - these two bones together are known as the hind-foot.
It is the Talus bone that joins the foot to the leg at the ankle joint which produces a hinge-like movement for the foot on the leg.
Figure 4 shows the bones of the foot grouped together.
Further down the foot situated in front of the hind-foot bones is what is known as the mid-foot. This area is made up of five bones closely linked together. This area is responsible for a lot of the shock absorption of the foot. You can see from the diagram that the bones fit together really well and that there are lots of joints between them.
In front of the mid-foot are five Metatarsal bones each of which leads to the toes – together this is known as the forefoot which acts like a lever when walking or running.
There are over 30 joints in your foot and each of these joints has a bag or more correctly a joint capsule surrounding it.
There are special thickenings in the joint capsule which help to strengthen the joints and prevent excessive movements – these are known as ligaments.
These ligaments along with other specialised thickened tissues known as fascia act passively to hold your foot together.
The ligaments actually work so well that you don’t need to use any muscles to support the foot while standing still! However when you move about and start to walk or run you need muscles to work to help support the arches in your foot.
The names of these muscles in the foot and ankle are not important at this fundamental level but you need to understand that there are two different groups of muscles acting on the foot.
There are the long muscles which start in the lower leg and then form long cords called tendons which pass around the ankle joint and then these split to attach to various bones in your foot.
These muscles are known as extrinsic – i.e. acting from outside your foot.
Figure 6 (The doted lines represent the tendon running under the foot)
The other class of muscles are known as intrinsic meaning both ends of each muscle are attached to bones in your foot. There are many intrinsic muscles in your foot, the larger ones tend to be found on the sole of your foot and they help to control the forefoot and assist with supporting the inner, and to a lesser extent, the outer longitudinal arches. There are small intrinsic muscles fitted between the bones of the forefoot and they help to control movements of your toes.
The transverse arch is supported by these intrinsic muscles and also two extrinsic muscles whose tendons cross the sole of your foot – the main one from inside to outside, and the second one from outside to inside. These two tendons together form the equivalent of a stirrup under the mid-foot.
As you can see from figure 6 the yellow tendon passes from the outside of your foot right across to the metatarsal of the big toe. The green tendon runs from the inside of the ankle joint and attaches to most of the bones of the mid-foot reaching across as far as the metatarsal of the 4th toe. You can visualise how these tendons support the arches of your foot like a stirrup. A few other extrinsic muscles cross the ankle supporting the arches to a lesser extent.
Figure 7 shows all the extrinsic muscles whose tendons cross the ankle joint and you can clearly see how the tendons on the inside of the foot help to support the inner longitudinal arch.
The extrinsic muscles on the front of your ankle help to pull up your toes and foot at the ankle.
Your foot’s main functions are to provide a way of contacting the ground, and to provide a platform from which to propel yourself forward. Put simply it is to be able to walk (and run) on surfaces ranging from soft shifting sand, through uneven rocky or woodland trails to running tracks and even hard concrete. The ability to conform to a surface is provided by the coordinated action of the intrinsic muscles.
To understand how the foot structure changes in a single stride let me try to explain what happens when you are walking. In walking and for a large number of runners the first contact with the ground is made by the outer aspect of your heel and your foot is rigid at this point.
The contact with the ground then moves along the outer border of your foot.
At this point your foot becomes flexible and your arches flatten enabling the area of contact to move across the base of the toes from the outside to the big toe.
Now the full of the front of the foot is in contact with the ground which is ideal for shock absorption and to aid balance. At this point there is maximum foot contact with the ground.
From this point your weight goes forward and your heel starts to lift off. It is just before this stage that your intrinsic muscles are working hard to adapt to the surface to keep as much of your fore-foot as possible in contact with the ground.
As your heel lifts and the energy stored in your leg muscles is released to move you forwards you need to have a stiff foot so that these forces can be efficiently transferred to the ground. If your foot was still soft and flexible you would not be able to transfer these forces and you would go nowhere fast.
To stiffen your foot you need the extrinsic and intrinsic muscle to work in a co-ordinated way to pull up the arch on the inside of your foot – this makes the foot relatively rigid and great for transferring force.
As your foot then leaves the ground it relaxes as it swings through the air in preparation for the next contact with the ground.
So as you now see you need both a flexible foot for shock absorption and uneven surfaces and a rigid foot for force transfer. Having a flexible foot is easy for 90% of us, however with fatigue, being overweight, bad posture and lack of exercise it is possible to lose the ability to adequately stiffen your foot at the correct time. This results in ‘flat feet’, an inefficient running style which can lead to injury at some point in the future!
HOW TO RECOGNISE YOUR FOOT TYPE
The easy way is to wet your feet and then stand upright with your feet comfortably apart on a flat dry surface that will allow you to examine the footprints that you leave as you carefully step away. You may need some dry paper – it is easier if the paper is dark. Quite often a shiny flat floor is adequate.
This can be quite an accurate test for those who have a high arched foot but this accounts for less than 10% of the population. For the rest of us we fall somewhere between normal and low-arched. Flat-footed is actually quite rare, probably less than 5% have no inner arch at all.
If you have a high-arched foot then you have problems with flexibility and shock absorption and you need shoes which compensate for this. If you have a low-arched foot then you need shoes with support. In fact you may need to see a specialist to get prescription insoles made that bring the ground up to meet your feet and this will help to reduce your tendency towards being injured.
You now have a good working knowledge of how your foot is made up including: –
- the structure of the two longitudinal arches
- the transverse arch
- how the bones fit together
- how ligaments and joint capsules hold the joints together
- how the muscles work together to support the arches
- the muscle groups that work on your foot – intrinsic and extrinsic
- how to recognise your foot type
- special shoe needs of the high-arched or low-arched foot
I want to thank you for taking the time to read this post and I would value any comments that you have to make.
Now you need to read part two of the series Ankle Joint – A Balanced View
See you there.
This entry was posted on Wednesday, August 19th, 2009 at 5:14 pm and is filed under Ankle and Foot, Foot. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.