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What happens in one part of the skeleton automatically affects other parts of it. When the foot pronates, the weight-bearing bone in the shin (the tibia) rotates towards the other leg. This stabilizes the knee joint to bear weight while taking a step, but when it happens too often or for too long – as in excessive pronation – it puts stress on the knee, causing pain.
The twisting motion can also be passed via the thigh bone (which is part of the knee joint) to the hip joint, causing pain. The disruption to the normal pattern of walking can be transmitted up the body via the skeleton, to the back and neck, causing pain.
So is it better to be a supinator?
A supinated foot has a characteristically high arch and spends an excessive amount of time on the outer (lateral) rather than on the medial (arch) border of the foot (as in the case of pronators). Supinated feet pronate very minimally. As they are the opposite of the flat-footed pronator, it might be reasonable to assume they avoid foot problems. But this is not the case.
Pronation is an important component of normal walking as it enables the foot to absorb shock when coming into contact with the ground and taking the weight of the body. Because of a reduced ability to pronate, the supinated foot is less able to absorb shock and consequently can be more susceptible to injury.
What other problems can be associated with flat feet?
The arch is held up by similar engineering principles to those which keep bridges up – the use of a ‘keystone’ kept in place by the surrounding bones. It is also maintained with tensioning applied by the tendon of the tibialis posterior muscle, which is found in the calf. But trauma – such as falling off a kerb – or physical changes such as increasing age or weight, can cause this tendon to give way causing the arch to suddenly drop. The resulting change in foot function nearly always causes painful problems.
Diabetes is associated with a neurological (affecting nerves) condition called Charcot’s Neuroarthropathy. This leads to loss of feeling in the feet, and often painless but serious changes in foot structure including complete flattening of the arch. Sometimes the arch bulges in the opposite direction leading to ulceration as the bulge is subjected to the pressure of walking.
So is having flat feet really a problem?
If the arches have always been low, there is every chance that they will never cause any problems. Even when associated with excessive pronation flat feet may function perfectly.
Flat feet which occur later in life, especially suddenly, as a result of trauma or other medical conditions like diabetes, are almost certain to cause big problems.