For more than 60 years, both custom and over-the-counter orthotics have been used for treating and preventing injuries in individuals with either high or low arches. Protecting this population from injury is important, as a 2019 study of 600 novice runners showed that runners with low arches were nearly 20 times more likely to be injured than runners with neutral arches, and runners with high arches were nearly 80 times more likely to be injured than neutral arched runners (1). Historically, these injuries have been successfully managed with both custom and over-the-counter orthotics, which have been proven to decrease the velocity and range of pronation, lessen tibial internal rotation, improve shock absorption, and decrease strain in the foot and ankle musculature (2,3). The high patient satisfaction rates and improved clinical outcomes associated with orthotic intervention explains why more than 80% of sports doctors routinely prescribe orthotics for their patient population.
There are, however, a few serious drawbacks to the widespread use of orthotics. One obvious downside is the cost: because of high laboratory fees and the time spent casting and dispensing orthotics, it’s not uncommon for doctors to charge $400 for a pair of custom orthotics. Another more significant problem is that orthotics can cause appreciable atrophy of the arch muscles. To prove this, researchers from Canada used ultrasonography to measure arch muscle volume before and after a 12-week study in which young adults wore custom orthotics. At the end of the study, the volume of the abductor hallicus muscles decreased by more than 17%, while their flexor digitorum brevis muscles decreased in volume by 10%. Atrophy of these muscles is extremely important as abductor hallicus atrophy correlates with the development of bunions, and flexor digitorum brevis atrophy correlates with the development of plantar fasciitis and impaired athletic performance (Fig. 1). Apparently, the excessive arch elevation present in custom orthotics offloads the intrinsic arch muscles so effectively that these important muscles atrophy from disuse.
The obvious solution to prevent orthotic-induced weakness of the arch is to recommend strengthening exercises when prescribing orthotics. The problem with strengthening exercises is that they are time-consuming and compliance is low.
An inexpensive alternative to orthotics that does not risk weakening the arch is to prescribe varus and valgus posts that do not support the arch in any way. In the last few years, a growing body of research is showing that the simple addition of wedged insoles produces all the favorable advantages associated with orthotic intervention, without the significant risks associated with supporting the arch. For example, early research out of Japan showed that valgus wedges placed beneath the outer side of a patient’s insole reduced the adduction moment at the knee, significantly lessening discomfort associated with medial knee arthritis (5) (Fig. 2). More recent research has shown that valgus wedges reduce compression of the medial knee by 4 to 12% compared to barefoot or shoes alone (6,7,8). Patients who had the best responses to valgus wedges were younger, had a lower body mass index and presented with less severe arthritis (9,10). Post angles as low as 4° were shown to significantly reduce compression of the medial knee, and this low angle is unlikely to cause discomfort elsewhere in the kinetic chain (11).
Valgus posting placed beneath the forefoot alone has also been shown to be an effective method of managing plan- tar fasciitis. To prove this, Kogler et al. (12) surgically inserted strain gauges into the plantar fasciae of 9 cadaveric feet and placed angled wedges beneath the foot in a variety of locations before axially loading each foot with up to
900 newtons applied through the tibia. Strain gauge measurements revealed that placing an angled wedge beneath the lateral forefoot significantly reduced strain in the plantar fascia by locking the calcaneocuboid joint thereby offloading the plantar fascia.
Varus posting has also been proven to significantly improve lower extremity motion. Stackhouse et al. (13) demonstrate that varus posts placed beneath insoles reduce the overall range of rearfoot pronation, lessen internal tibial rotation, and decrease the velocity of knee flexion during stance. All of these biomechanical findings have the potential to greatly reduce the risk of knee injury. In another interesting study, Joseph et al. (14) had 10 female Division I college athletes perform a drop jump test while wearing a conventional flat insole, or an insole modified with a full-length 5° varus wedge. Subsequent three-dimensional motion analysis confirmed that the varus posts reduced knee valgus at initial contact, reduced the maximum knee valgus angle, and decreased ankle pronation during initial ground contact (Fig.3).
Fig. 3. By reducing the range of internal tibial rotation and decreasing the velocity of knee flexion, varus posts can reduce valgus collapse of the knee and ankle (A and B). The 2-piece Peel and Stick Varus Posts (C and D) allow you to post the forefoot and/or the rearfoot.
These findings are extremely important because excessive knee valgus on landing is strongly correlated with the development of a wide range of injuries, including anterior cruciate ligament tears. One of the more interesting aspects of this article is that the authors prescribed full length varus posts regardless of the patient’s foot architecture: both high and low arched individuals were treated with the same varus posts and had the same outcomes. The universal positive effect of varus posts is important because it takes the guesswork out of deciding which patients with valgus collapse might benefit the most from varus posts.
Interestingly, in an extensive 2018 literature review evaluating the ability of different components of an orthotic to alter lower limb movement patterns, researchers from the University of Montréal concluded that flat orthotics possessing arch support alone provided no control of lower extremity motion, while insoles possessing medial posting in either the rearfoot and/or forefoot significantly reduced foot pronation (15). The authors state that “using me- dial posting is the most effective foot orthotic feature to reduce the peak rearfoot eversion and to control excessive
foot pronation.” The findings of the 2018 literature review were corroborated in 2019 study in which researchers evaluated 3-dimensional motion as subjects wore either a flat insole with an arch support, or the same insole possessing a 7° varus wedge. Results of this study conclusively confirmed that wedged insoles more effectively reduce foot and ankle pronation, decrease internal rotation of the knee and hip, reduce hip abduction, and significantly lessen stress on the muscles responsible for decelerating pronation (16). The one caveat for using varus posts is that just as valgus posts can offload the medial knee, varus posts can increase pressure in the medial knee by causing the tibia to adduct in the frontal plane (16). As a result, varus posts should be used cautiously in individuals with medial knee osteoarthritis.
Taken together, the latest research shows that varus and valgus posts can play an important role in altering mechanics and/or preventing injuries. This is especially true for managing valgus collapse of the knee, lessening patellofemoral pressure, and/or improving alignment of the foot and leg. Unlike custom and over-the-counter orthotics, these posts do not physically support the arch, and will not cause disuse atrophy of intrinsic muscles of the foot. Peel and Stick Posts are inexpensive, easy to apply, and should be a part of every practitioner’s clinical toolbox.
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