Nearly a third of Americans will develop osteoarthritis of the knee before age 70. Beside knee replacement, most people resort to pain pills. Assistive devices such as wedge insoles, therapeutic cushions, bipolar magnets and orthortics are often prescribed as a less drastic, side effect-free treatment option. But do they really work?
Humans and bipedal hominids have been running for millions of years, and of course for most of that time that humans have been on earth, we ran barefoot. Modern running shoes were actually only invented in the 1970s. Since that time, back, hip, knee and ankle overuse injuries, including tendonitis, and muscle disorders have only increased. So health experts came up with what they thought was a novel approach--namely that "we need more support from our footwear." Nothing could be further from the truth.
Wearing Anything Specialized On Your Feet Alters Normal Form And Function Of The Foot
A habitually shod lifestyle has consequences for the biologically normal anatomy and function of the foot.
Kristiaan D’Aout and Peter Aerts from the Biology Department at the University of Antwerp collaborated for their work on the biomechanics of barefoot walking with Dirk De Clercq (University of Gent, Belgium) and with Todd Pataky (University of Liverpool, UK).
This team made the first detailed analysis of foot function in people who have never worn shoes. For this project, they travelled to South India, where many people walk barefoot throughout life, mostly for spiritual or financial reasons.
In this way, the researchers wanted to gain an insight into the biologically normal function of the foot, which evolved for millions of years - unshod.
The research was funded by the Fund for Scientific Research - Flanders, and was based on dynamic measurements of pressure distribution under to foot sole during walking. It showed that he foot of habitual barefoot walkers differs, both in shape and in function, from that of habitually shod peers.
Barefooters have a relatively wide forefoot and manage at better distributing pressures over the entire surface of the foot sole, resulting in lower (and most likely favourable) peak pressures. As such, the fundamental scientific results are also important for clinicians and for the design of quality footwear, which should not hamper the foot’s biologically normal function.
A research review published today in JAMA indicates that these shoe inserts do little--if anything--to relieve arthritis pain.
The review looked at the use of specialized orthotic wedge insoles for medial knee osteoarthritis, which affects the inner part of the knee. Lateral insoles are thicker at the outer edge of the foot. Slightly tilting the foot is thought to reduce the load on the inner knee joint.
Walking directs more force to the inside part of the knee (the medial aspect) than the outside part (the lateral aspect). The medial compartment is where osteoarthritis usually appears first. “A lateral wedge insole is intended to reduce pressure transmitted through the lower leg to the medial compartment of the knee during walking,” explains Dr. Robert Shmerling, clinical chief in the Division of Rheumatology at Beth Israel Deaconess Medical Center, and associate professor of medicine at Harvard Medical School.
To see whether lateral wedge insoles actually relieve arthritis pain, an international team of researchers evaluated the results of 12 different shoe-based clinical trials that included a total of 885 participants. Trials comparing the lateral wedge insole to a neutral insole didn’t find a significant improvement in pain.
The cost of lateral wedge insoles can range from $10 for ones you buy off the shelf at your local pharmacy or shoe store to $500 for a pair of custom-made insoles your podiatrist or orthopedist orders for you. “Considering the results of this study, I think it’s hard to justify a big investment in wedge insoles solely to treat knee pain from osteoarthritis,” Dr. Shmerling says. “My advice would be to go with inexpensive insoles, and if you’re no better, and if nothing else is working, you could consider seeing a podiatrist or orthotist for higher-end options.”
Biomechanics of the Foot Strike
Your feet are your connection to the ground. What that said, there’s a lot of prerequisites that go into performing your movements. One of the functions that the foot has that’s of particular interest is that it’s a base of support; whether it be in a single stance, as you would be if you’re sprinting, or in a double stance if you are walking, squatting, or other basics.
The second component to it is that it’s a mechanism for leverage to create propulsion. And for propulsion to occur: 1) There must be contact with the ground and it has to act as a base of support in order for that to happen. and; 2) The other component that the foot has or is responsible for is shock absorption. You cannot propel yourself and not be able to absorb the impact at contact. Those four functions that the foot has are all intertwined, so no one function is superior to the other. It’s the sum of all functions that creates a superior foot.
A typical sequence for foot function regardless of if you’re walking, if you’re jogging, if you’re running or sprinting, is that with your foot, the initial contact is with the outside of your heels first. The second step that occurs is what we call pronation; that’s where your foot starts to flatten, if you will. That mechanism there is essential because that is where a lot of force absorption, absorbing impact at contact occurs, but also too, its second function there is to set up the foot for the final phases of contact with the ground.
The third step after pronation is supination; this is where your arch starts to increase in height, which permits rigidity in the foot to allow you to toe-off, which is the final stage where your toe-off, in the true sense of the word, should occur between the first and second toe. Most people land on the heel and pronate but they pronate either too soon, too abruptly, or it’s sustained too long so that their foot is forced to rush into supination. In doing so, it’s almost like a flicking mechanism where you end up toeing-off on the outside of your foot.
Supportive Footwear and Orthotics May Be Your Source of Pain
Other support systems besides the foot itself will aggrevate this problem for many. When you remove the primary support system of the foot and use supportive devices instead, everything relating the lower body joints becomes weak. This includes the ankle, knee, hip and even lower back. It affects everything. What essentially occurs when you use supportive devices such as cushioned footwear and orthotics is that you interfere with the normal neural processing that is meant to occur between the point of impact and propulsion. This dramatically and detrimentally affects the natural development of the joints and their strength. If we compare the joint and muscle strength of feet and ankles of those in developed societies to those in underdeveloped societies such as in Africa, there is a substantial difference in the development of these joints and muscles.
One of the problems with using performance footwear is that once they’re out of the support, they don’t necessarily use their foot correctly to initiate a lot of the basic movements, including walking for that matter. So they run into an issue where they don’t really use the foot and they’re more from-the-knee-up dominant versus athletes such as distance runners or recreational runners.
They have a tendency to just use the foot passively in the sense that it’s there just to make contact and you just are going through the motions with your legs. The foot actually has an integral part to a toe-off which most people won’t use. And sometimes shoe wear and potentially orthotics can actually hamper that dysfunction.
The whole scenario whether it be a weight belt, orthotics, or potentially certain types of footwear, is that our body is meant to respond to a stimulus, a change if you will, and that change or stimulus has a threshold for stimulating the body. Once you’ve reached that threshold, which in each person is a slightly different, the body decides to shut off because it knows that something else is doing the work and many times that’s where people run into problems. That dependence now becomes or supersedes a lot of what they’re doing in their training or daily lives. It becomes a crutch that does not address the root causes of dysfunction in gait, muscle strength ratios and other biomechanical deficits. The well-intentioned use of orthotics may actually backfire for a large percentage of the population.
Tammy McKenzie is a certified personal trainer and fitness specialist with a speciality in women's fitness.