Inventor and Designer of Postural Control Insoles

Etiology of the Flexible Flat Foot

The flexible flat foot is not a cause in of itself.  It is merely a symptom of an underlying cause.  The most frequent causes cited in the literature for flexible flat feet are:

  • Weakening of the tendon in the foot (e.g., Posterior Tibial Tendonitis, Ehler-Danlos Syndrome)
  • Weakening of the muscles in the foot (e.g., Myasthenia Gravis, Muscular Dystrophy)
  • Nerve injuries (e.g., Multiple Sclerosis)
  • Injury to the foot
  • In 2002, another cause of the flexible flat foot was described, which was previously unknown (Rothbart 2002).

To read about this previously unknown cause of a flexible flat foot, download:

​          Rothbart BA 2009. What exactly is a Flatfoot? Are there different types?   Podiatry Review, Vol 66(6):4-6.

Another way to determine if you have a flexible flat foot is to take the Footprint Test:

Foot imprint made by a flexible flat foot

Vertical Talus Syndrome

When you get out of a swimming pool, look at your footprint on the concrete.  The front of the foot (the ball) should joint the heel by a strip, ideally, this strip should be about 1/2 the width of the ball of the foot.  If your foot is flat, then the strip is the same width as the ball of the foot, creating a footprint that looks like a stretched out pancake (hence the expression, flat as a pancake).

However, when you sit down and take the weight off your feet, your foot will have an inner arch.

The structural flat foot is like a level foundation of a building.  It is very stable and solid and generally requires no treatment.

In this post, I am going to talk about the flexible flatfoot, which is not stable and so can lead to symptoms in the body including muscle and joint pain as well as visceral symptoms.

Structural Flat Foot

If you do a Google Search on Flat Feet, you will be supplied with a staggering number of hits; 763,000,000 to be exact (as of July 09, 2019).  Let's take a look at this foot structure that obviously affects many people.

What exactly is a flat foot

A flat Foot, or Pes Planus, is a term given to a foot that has lost its arch and is flat.

There are two distinct types of flat feet:

(1)  The structural (or rigid) flatfoot - the inner longitudinal arch is always flat (sitting, standing or walking)

Toe Raise Test

  • Inner arch is totally flat when standing or walking
  • Inner arch is intact when weight is removed from the inner arch

Etiology of a Flat Foot

The structural flat foot is not a cause in of itself.  It is merely a symptom of an underlying cause which is usually present at birth.  Some of the causes cited in the literature for structural flat feet are:

  • Normal genetic variances, e.g., low calcaneal angle
  • Tarsal Coalitions (Want 2008, Vu 2007)
  • Vertical Talus Syndrome (Rothbart 1974)

  • Bartenwerfer Syndrome and Rubinstein-Taybi Syndrome (both relatively rare syndromes)

(2)  The flexible flat foot - the inner longitudinal arch is flatter (or completely flat) only when weight is put on the foot (e.g., standing or walking), but intact when weight is take off the foot. (See Toe Raise Test below)

What Exactly is a Flatfoot?  July 09, 2019