Practice Perfect 668
Biomechanical Decision Making
The KK Approach
Part 2 - Nonsurgical Pathology

In Part 1 of our biomechanical decision making discussion, I introduced a reformulation and combination of prior methods to create the kineticokinematic, or KK approach. The KK approach asks us to identify the specific anatomic structure that is damaged (via the history and physical), determine the biomechanical causes of that damage (via the physical examination combined with a proper understanding of the biomechanical research), and then focusing treatment on those biomechanical causes. In today’s edition, let’s take a look at how this method will help us treat a very common condition, plantar fasciitis. We’ll emphasize the nonsurgical side of treatment today and then examine surgical treatments of other diagnoses in the near future. As a quick disclaimer, much research has been performed on plantar fasciitis, and a fully comprehensive discussion is beyond the scope of today’s discussion.

The KK Approach to Plantar Fasciitis

Obtaining a complete history and physical examination identifies plantar medial heel pain on first step after rest (poststatic dyskinesia) as a pathognomonic symptom. Extrinsic factors such as shoe gear, weight, and work environment are additionally important, as they have been found to be contributors1. The physical examination makes the diagnosis rather quickly with plantar medial heel pain to palpation, identifying the plantar fascia as the damaged anatomic structure.

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However, step two of the KK method – determining the biomechanical contributions to the damaged plantar fascia – is pivotal. Conceptually, anything causing extra strain or stress on the plantar fascia will cause injury and degeneration over time. This is, in fact, the true pathology of plantar fascial pain. Rather than being an inflammatory disorder (fasciitis), this condition is traumatic and degenerative in nature and is more correctly termed plantar fasciosis2.

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As I mentioned, anything causing stress to the fascia will lead to degeneration and pain, and it so happens that several biomechanical factors can overload the plantar fascia. The type of foot is an important contributor. Pes planus foot types with a pronated subtalar joint and increased medial column mobility will cause elevation of the medial column, especially during the push off period of the stance phase. Elevation increases the origin-to-insertion distance of the plantar fascia, causing increased pull. Similarly, a high arched pes cavus foot type with a flexible arch (termed flexible forefoot valgus) also leads to elevation of the medial arch while walking (without the magnitude of subtalar pronation as seen in pes planus) and the same tension on the plantar fascia as that seen in the flatfooted condition. It’s not surprising, then, that an everted heel1,3 (seen in pes planus as part of subtalar pronation) and ankle equinus1 have both been associated with plantar fascial pain, since both are associated with arch elevation. Other mechanical contributions such as leg length discrepancy and knock knees (genu valgum) must also be considered.

Plantar Fasciitis Treatment Using the KK Approach

Treatment of this disorder, then, is aimed at relieving strain on the plantar fascia by addressing these biomechanical causes. Obviously, extrinsic factors such as obesity and nonsupportive shoe gear must be addressed. Shoes with adequate torsional control will provide some support. Weight loss via diet modification, exercise, and counseling achieves a 5% weight loss versus usual care4. Other treatments for plantar fasciitis based on this method include night splints to reduce the ankle equinus5 and stretching exercises. In a similar vein, corticosteroid injections should be considered a temporary pain-relieving method rather than addressing the cause, since plantar fasciosis is not inflammatory in nature.

Many custom foot orthosis modifications potentially relieve strain on the plantar fascia, though this is hardly well studied. Fully realizing the potential of the KK approach will require us to know exactly what kinetic and kinematic effects various orthosis modifications have on the lower extremity. For example, Scherer and colleagues found first metatarsophalangeal joint dorsiflexion to be increased by 90% with foot orthoses and a casting method that plantarflexed the medial column (kinematic modification)6. Similarly, Kogler et al determined that only a wedge placed under the lateral forefoot deceased strain on the plantar fascia. Rearfoot varus wedges did nothing to plantar fascial strain while forefoot varus wedges actually increased strain (kinetic changes)7. For those of you attempting to support a forefoot supinatus with a forefoot varus post (a common method advocated by the Rootian system to accommodate this deformity) you may actually be making matters worse since this maintains the medial column in a dorsiflexed position.

It would be helpful for us to know fully the effects of orthosis modifications. How much rotational force do various medial heel skives place on the foot? What heel lift height is the limit before placing too much force on the forefoot? When should medial flanges be used? How much lateral weight and force transfer does a first metatarsal head cut out actually cause? These questions and many others have yet to be answered.

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Using the KK approach, my foot orthosis prescription for plantar fasciitis in the pes planus patient is as follows:

  • Plaster nonweightbearing casting with the medial column plantarflexed and holding the foot not in neutral position but rather corrected position, with the rearfoot perpendicular to the leg.
  • Functional orthosis with a stiff shell of standard width.
  • Rearfoot varus post (to correct heel valgus).
  • Minimal cast fill to hug the arch as closely as possible.
  • Deep heel cup with medial heel skive (to increase orthosis reactive force medial to the subtalar joint axis).
  • First metatarsal head cut out (to increase medial arch plantarflexion).
  • Forefoot valgus post .
  • Seven mm heel lift to both sides if ankle dorsiflexion is very restricted. If there is a leg length difference then the lift will differ to balance the sides.

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There are many other prescriptions and modifications that may be just as helpful, but until relatively recently the only indicators we had of success were subjective clinical improvements by patient report and the appearance of a rectus foot while standing. It’s time to go beyond that with the KK approach.

Best wishes.

Jarrod Shapiro, DPM
PRESENT Practice Perfect Editor
jarrod@podiatry.com
References
  1. Riddle DL, Pulsic M, Pidcoe P, Johnson RE. Risk factors for Plantar fasciitis: a matched case-control study. J Bone Joint Surg Am. 2003; 85:872-877.
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  2. Lemont H, Ammirati KM, Usen N. Plantar fasciitis: a degenerative process (fasciosis) without inflammation. J Am Podiatr Med Assoc. 2003 May-Jun;93(3):234-237.
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  3. Chang RR, Rodriguez PA, Van Emmerik REA, Hamill J. Multi-segment foot kinematics and ground reaction forces during gait of individuals with plantar fasciitis. J Biomech.Aug 22;47(11): 2571-2577.
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  4. LeBlanc ES, Patnode CD, Webber EM, et al. Behavioral and Pharmacotherapy Weight Loss Interventions to Prevent Obesity-Related Morbidity and Mortality in Adults: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA. 2018;320(11):1172-1191.
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  5. Batt ME, Tanji JL, Skattim N. Plantar fasciitis: a prospective randomized clinical trial of the tension night splint. Clin J Sport Med. 1996 Jul;6(3):158–62.
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  6. Sherer PR, Sanders J, Eldredge DE, et al. Effect of functional foot orthoses on first metatarsophalangeal joint dorsiflexion in stance and gait. J Am Podiatr Med Assoc. 2006 Nov-Dec;96(6):474-481.
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  7. Kogler GF, Veer EB, Solomonidis SE, Paul JP. The influence of medial and lateral placement of orthotic wedges on loading of the plantar aponeurosis. J Bone Joint Surg Am. 1999 Oct;81(10):1403-1413.
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