Pronation, Supination and Shoe Selection
Pronation of the foot is a normal process that occurs when your foot makes contact with the ground. More specifically your ankle and foot will normally pronate 6 to 8 degrees during midstance (Mann RA: Biomechanics of running. Academy of Orthopedic Surgeons, St. Louis, 1982). Pronation can be described as the inward collapse of the ankle and the arch flattening. Foot pronation is necessary in order for the foot to adapt to uneven surfaces. The more the foot and ankle pronates, the more the tibia (leg) internally rotates. Excessive tibial rotation negatively affects the knees and hips and can lead to overuse injuries like ITB syndrome, shin splints and knee problems. Long term this may lead to muscle imbalances and postural compensations that may place the runner at risk for more serious pathologies such as stress fractures and degenerative joint disease, especially of the knees and hips (Arnheim: Modern Principles of Athletic Training, 1989).
In order to better understand pronation, or more specifically excessive pronation, one must ask the question, how much pronation is considered normal? How much pronation will put me at greater risk of injury? When do I choose a stability shoe vs. a cushion shoe or a motion control shoe to help prevent excessive pronation? As the owner of the San Diego Running Institute, I have attempted to answer these and other questions by performing literature searches using the National Library of Medicine which archives all accepted published research by the medical and podiatric communities. Surprisingly I have found little if any documentation or evidence to support many commonly held beliefs regarding pronation. In fact I have discovered much misinformation on the subject. For example, when looking to find what degree of pronation is considered a risk factor for running injuries there appears to be much controversy. A leading orthopedic textbook states that mild pronation can be defined by the foot rolling inward 4 to 6 degrees, moderate pronation 6 to 10 degrees and severe pronation of 10 to 15 degrees. Yet David Brody MD, in his clinical symposium on running injuries stated that over 2-3 degrees was to be considered hyperpronation. He also suggested measuring for navicular drop. He states that a distance of 15 mm from non weight bearing (sitting) to weight bearing (standing) should be considered hyperpronation and in a symptomatic patient indicates the need for an orthotic device.
Through the research, I have created a scientific systematic way of fitting runners. I have developed a shoe fitting process that takes into account a runner’s entire kinetic chain from their foot to their hips. Pronation is measured taking into account rearfoot eversion, navicular drop, foot shape, body weight, leg length discrepancy, pelvic rotation, muscular balance/imbalance and pre-existing injuries. After compiling the findings shoes are selected for the runner to try. The runner then tries the shoes on a treadmill to ensure comfort. Studies (Nigg: Medicine & Science in Sports and Exercise, 2003) suggest comfort to be an important and relevant feature in choosing shoes and foot orthoses. It was found that comfort was directly related to differences in functional biomechanical variables. In other words if the shoe is not comfortable within minutes it will not be comfortable the next day or the day after that. We have all heard a salesman say “they will feel better after they break in”. Based on current research this statement should be questioned. I have had the personal experience of trying on every shoe in the store. I tried them sitting, standing, walking and running. One constant always held true. If they did not feel comfortable while sitting they would never feel comfortable walking and especially not while running.
In order to better understand pronation and shoes it is necessary to explain shoe technology. While shoe companies will continue to add and change the names to make them more appealing to the general consumer, there remains three basic shoe types. Cushion, stability and motion control. Cushion shoes are thought to go with high arch feet (Pes cavus) and possibly neutral feet. Stability shoes are generally selected for mild pronators and motion control for severe pronators. But you have to ask, am I a mild pronator or severe? What measurement constitutes mild? Moderate? Severe? In most shoe stores the employee subjectively selects the shoe based on their unscientific, misinformed subjective opinion. Many times motion control shoes are selected for runners with neutral feet! In addition there is a distinct difference in static posture, walking gait and running gait. The biomechanics in walking vs. running vs. sprinting gait have been studied and found to be radically different. We also have to take into account that some runners are “toe” runners, meaning they do not heel strike. So even if they display a large degree of pronation in static posture putting them in a more expensive motion control shoe would be useless as the heel counter does not control the toe box.
As you can see, finding the best shoe for you is not an easy task. There is a great deal of mis-information out there and a lot of well meaning, under-informed sales people. To ensure you are getting the best shoe for your foot and running style go to a well qualified shoe fitting specialist. They should perform a series of measurements and tests prior to selecting a shoe category for you and should present you with multiple options in order to assure a comfortable fit. If you do not feel that you are in capable hands, be very wary about your purchase as improperly fit shoes can lead to running injuries on the road.
Minimize the risk of injuries and raise up the level of your game by having custom running shoe fitting.
Written by Dr. Victor J Runco, DC