Flat Feet

What is a Flat Foot?

A ‘flat foot’ is as the name suggests a foot with a reduced arch which appears ‘flat’. A foot may be so flat the complete sole of the foot may touch the ground.

The correct anatomical name for a flat foot is a ‘pes planus’ foot posture.

Why do people have flat feet?

There are a number of reason why people might have a flat foot

Hyper mobile joints the normal ligaments and joints that support the arch of the foot may move more than they should – this means when someone stands the arch can no longer support itself and the foot collapses
Tibialis posterior tendon dysfunction  – The tibialis posterior muscle and tendon supports the arch of the foot
Children – It is normal for children to have a flat foot as they are developing. This is due to the increased mobility in the joints and the fact that the bones in the foot are not fully formed
Over weight – Increased weight may overload the normal structures that support the arch resulting in its collapse
Genetics- Sometimes having flat feet can run in the family. Generally this is due to the genetic link between ligament laxity running in families.

What is the problem with having flat feet?

There is nothing wrong with having a flat foot but in some people it can result in a number of long term problems. These include:

Tibialis posterior tendon overuse

This is because the position of the foot changes the demand from certain muscle groups.

Neutral Foot In a neutral foot  the muscles on the inside of the foot (invertors) work just as hard as the muscles on the outside of the foot (evertors).
Flat Foot In a flat foot the muscles on the inside of the foot (invertors) work a lot harder to try and correct the position of the foot  – overtime this can result the degeneration of the tibialis posterior tendon.

Dorsal Midfoot compression

Sinus tarsi pain

When the foot is neutral the sinus tarsi is aligned and there is no compression of the tissues. When the foot is flat or pronated the sinus tarsi is compressed and can cause pain (sinus tarsi syndrome.

Ankle Arthrtitis 

Great toe joint dysfunction

In a normal arched foot the 1st metatarsal is plantar flexed. This allows the great toe to function normally and there is no jamming.
In a flat arched foot the 1st metatarsal is dorsiflexed. This causes dorsal jamming of the great toe

Orthotic Treatment of flat feet?

There are a number of different orthotic designs available for flat feet. Most orthotic designs are simply arch supports.

These are not ideal for the flat foot, often only irritating the arch of the foot.

This is due to the subtalar joint axis position. The diagram below shoes the axis of the subtalar joint.

The most appropriate design for a flat foot is a rearfoot orthotic this type of orthotic applies pressure on the red area which increases the arch of the foot without causing discomfort as with most midfoot orthotics.