What Is A ‘Normal’ Foot?

Pages: 82 - 82
Author(s): 
Kevin A. Kirby, DPM

Podiatrists commonly use the terms “normal” and “abnormal” to describe foot structure and foot function. We might look at a set of plain film radiographs and note that one foot has a hallux valgus angle that we call “normal” while the contralateral foot has a hallux valgus angle that we call “abnormal.” We might also do gait examinations in our office and tell one patient that his gait appears normal while in another patient, we may say that her gait appears abnormal.

Regardless of how many times we use the terms “normal” and “abnormal” in our discussions with patients or other physicians, or in our lectures or written articles, these terms do not mean the same thing to all podiatrists. One podiatrist might think that an individual with only 7 degrees of ankle dorsiflexion with the knee extended during clinical examination has “normal” ankle dorsiflexion while another podiatrist might think that only 7 degrees of ankle dorsiflexion is “abnormal.”  

One of the problems regarding the terms “normal” and “abnormal” within the podiatric profession may have come from one of the earliest textbooks on podiatric biomechanics, Biomechanical Examination of the Foot, Volume 1. Merton Root, DPM, William Orien, DPM, John Weed, DPM, and Robert Hughes, DPM, published their book on biomechanical examination of the foot in 1971 and described a set of eight “Biophysical Criteria for Normalcy,” which they considered to be ideal values to allow normal foot function. Many podiatrists still commonly use these criteria to determine whether a foot is normal or abnormal.  

A few of the “criteria for normalcy” proposed by Root and colleagues include that the distal one-third of the leg is vertical, the subtalar joint rests in its neutral position and the calcaneal bisection is vertical during bipedal stance. Does this mean that when an individual stands with his calcaneus inverted 3 degrees from vertical that his foot is “abnormal”? Yes, it does, using the strict biophysical criteria for normalcy proposed by Root and colleagues.

The issue with the biophysical criteria for normalcy that Root and coworkers proposed over three decades ago is that scientific research has never shown these criteria to be either ideal or an average range of foot and lower extremity structural parameters within the healthy human population. This lack of research evidence within our profession supporting what exactly constitutes normal and abnormal structure and function causes confusion, and impedes professional communication since no two podiatrists can agree as to what a normal and abnormal foot exactly looks like or functions like.

With these facts in mind, the question that begs to be answered is whether we, as a profession, should be using the terms “normal” and “abnormal” to describe ideal foot and lower extremity structural parameters where only one ideal structural alignment can mean that the foot is “normal”? Do we use only one numerical value to describe any measurable parameter of the human body and then consider that one numerical value to be “normal” while all the other values are “abnormal”? Do we say that the only “normal” hematocrit for an adult male is 45 percent while hematocrits of 43 percent and 47 percent are “abnormal”? Do we say that the only “normal” fasting blood glucose test is 85 mg/dL and it is “abnormal” when it is either 75 or 95 mg/dL? Of course, we don’t.

In medicine, ranges of normal describe the accepted range of numerical values in healthy individuals, whether these numerical values are referring to blood tests, nerve conduction velocities or bone density tests. The rest of the medical world realizes that due to the diversity within the human population, there exists a range of measurable biological parameters within which individuals can live and function without disease or disability. They base these values on multiple scientific research studies on large groups to determine an average range of numerical values within healthy individuals. They do not limit their descriptions of “normal” to mean only one numerical value that is a theoretical ideal with not a shred of scientific research to support it.

The podiatric profession needs to collectively research and redefine the ranges of “normal” and “abnormal” foot structure and foot and lower extremity function. We can no longer rely on unsupported theories from over 30 years ago to define an ideal “normal” foot structure and foot function. We need to respond to this glaring lack of basic research in foot structure and function, if for no other reason than for the sake of our academic and professional integrity.

Dr. Kirby is an Adjunct Associate Professor within the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt University in Oakland, Calif. He is in private practice in Sacramento, Calif.

 

Comments

I just got back from the Vancouver PAC/PFOLA Biomechanics Conference and had the pleasure to speak again with my old friend from Sydney, Australia, Joshua Burns, PhD, who was one of the keynote speakers for the Conference.  I was delighted to hear that Josh is currently pursuing exactly the type of project that I discussed in my article on "What is a Normal Foot?" in the April 2015 issue of Podiatry Today magazine.

The name of his project is the 1,000 Norms Project and it involves gathering and compiling a normative database of a range of foot and lower extremity structural and functional parameters from healthy individuals of all ages to determine what exactly consitutues "normal" foot and lower extremity structure and function. This is one of the most exciting projects that I have seen in many years and I'm grateful that Dr. Burns is spearheading this project for the worldwide healthcare community.

For those interested in reading more about the 1,000 Norms Project, here is the website from the University of Sydney.  

http://sydney.edu.au/health-sciences/research/1000-norms.shtml

Cheers,

Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine

For those interested, here are some more articles coauthored by Josh Burns, PhD, on his 1,000 Norms Project based out of the University of Sydney, which is a long-term database gathering project designed to determine "normal" foot structure and function in 1,000 individuals from the ages of 3 to 100.

 http://bjsm.bmj.com/content/early/2015/04/14/bjsports-2014-094489.short?g=w_bjsm_ahead_tab 

http://www.physiotherapyjournal.com/article/S0031-9406%2815%2900005-X/abstract

 

 

1000 Norms Project

A deeper understanding of human variation is essential. The 1000 Norms Project is a ground-breaking research project currently generating great national and international interest. It involves measuring a range of strength, flexibility, alignment and physical performance indicators of 1,000 healthy people aged 3-100 years. An initiative of leading researchers at The University of Sydney, the aim of the project is to improve our understanding of the physical capabilities of the healthy population across the entire lifespan.

For those interested, I will be discussing this project at the Pint of Science festival on the 18th of May in Sydney, Australia: http://pintofscience.com.au/event/mind-syd-mon/

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