October 2019

Plantar fasciitis: A New Approach to An Old Problem

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Introducing the kineticokinematic approach to treating plantar fasciitis. This approach focuses not only on the position of the foot but also on the forces that may be contributing to this highly prevalent foot condition.

By Pedro Aldape-Esquivel, DPM and Jarrod Shapiro, DPM, FACPM, FACFAS

Heel pain is one of the most common complaints treated by lower extremity specialists, affecting an estimated 10% of the population.1 With this high prevalence of heel pain, different treatment approaches have emerged, with varying results. Nonsurgical options include stretching exercises, icing, nonsteroidal anti-inflammatory medications, taping, custom orthoses and prefabricated inserts, night splints, and corticosteroid injections. With this variety of treatments, about 90% of plantar fasciitis is resolved after 10 months.2 The other 10% of patients with persistent pain will usually undergo surgical treatment via a different variety of surgical methods.

Historically, treatment for plantar fasciitis has centered on the idea of supporting the plantar fascia by manipulating the foot into an “ideal position” to keep the medial arch from collapsing and preventing increased strain. However, most of the focus has been on the kinematics, or position, of the pedal architecture. Kinetic forces, or the forces that act on the foot, must also be considered in the treatment plan to improve symptoms.

This paper will present a new thought process to diagnose and treat lower extremity pathologies and, in this case, plantar fascial pain, termed the kineticokinematic approach (KK approach). This method focuses on both the position of the foot and the forces acting on it and advocates a 3-step approach.

  1. Determine the specific anatomical structure that is damaged or under strain.
  2. Clarify the underlying biomechanical causes.
  3. Treat the causes by adjusting forces (kinetics) or addressing deformities (kinematics).

The KK Approach to Diagnosing and Understanding Plantar Fasciitis

Plantar fasciitis is primarily a clinical diagnosis, which can be identified with a thorough history and physical examination. From the history, patients will report the hallmark post-static dyskinesia, or plantar heel pain after rest, which decreases after taking a few steps or spending more time on their feet. This phenomenon is believed to occur because of the lack of tension in a static non-weightbearing state; therefore the plantar fascia rests in a contracted state.3 Upon initial weightbearing, the plantar fascia undergoes a rapid increase in tension, initiating pain. In 2014, Sundararajan reported on a retrospective study of 40 patients without a previous history of plantar fasciitis who had undergone lower extremity surgery and were non-weightbearing for either 2–6 weeks (group 1) or 6–10 weeks (group 2). She found that 70% of group 2, the extended non-weightbearing group, developed post-static dyskinesia in the immediate weightbearing period. Following treatment with plantar fasciitis stretching exercises, 100% saw resolution of their symptoms, demonstrating a high sensitivity for this hallmark sign.3

Extrinsic factors such as high body mass index (BMI), hard floors, and poorly supportive shoe-wear have also been associated with plantar fasciitis. Riddle et al found an increased BMI significantly increased the risk of plantar fasciitis with an odds ratio of 5.6 at BMI greater than 30 kg/m2.1 Hard surfaces have been identified as a factor in the development of this condition in numerous studies of runners, assembly plant workers, and those doing extended weightbearing (eg, teachers, nurses). Although mostly anecdotal, shoes with poor arch support or “flats” will effectively allow the arch to collapse and lead to overpronation and heel pain.

Extrinsic factors such as high body mass index (BMI), hard floors, and poorly supportive shoe-wear have also been associated with plantar fasciitis.

A thorough physical examination confirms the plantar aponeurosis as the structure under tension while ruling out other differential diagnoses. This exam also provides significant information regarding the biomechanical etiologies of this diagnosis for which treatment may be targeted. The diagnosis of plantar fascial pain is typically easily confirmed when the patient reports pain with palpation of the medial plantar calcaneal tubercle. Discomfort may also be elicited with activation of the windlass mechanism, originally described by Hicks,4 which is performed by dorsiflexing the hallux at the 1st metatarsophalangeal joint causing shortening of the arch, thus increasing the tension of the plantar fascia.5 The plantar fascia is only capable of elongating by 4%,6 thereby creating high tensile forces that increase stress on the insertion at the calcaneus. However, one must be cautious using this test in isolation. De Garceau et al in 2003 performed the windlass test in patients with a history and physical exam consistent with plantar fasciitis and found the test had a sensitivity of 31.8% if performed weightbearing and 13.6% when performed non-weightbearing,7 concluding it is a poor test to diagnose plantar fasciitis.

Other differential diagnoses of heel pain must also be explored during the examination. A calcaneal squeeze test may indicate a calcaneal stress fracture as the etiology for the heel pain, although the authors commonly find this test falsely positive in many cases of plantar fasciitis. A positive Tinel’s sign and a history of paresthesia or shooting pain that radiates from the medial malleolus into the foot may lead to a neurologic diagnosis, such as tarsal tunnel syndrome, while a history of back pain and positive straight leg raise with dermatomal sensory and muscular changes increase the concern for lumbosacral radiculopathy.8 Tenderness to the posterior heel likely originates from the Achilles tendon, posterosuperior calcaneus, or adventitial bursa formation.

Radiographs can be helpful to rule out fractures and support biomechanical examination findings if taken while weightbearing. However, radiographs are unnecessary for the diagnosis of plantar fasciitis.4

Several biomechanical abnormalities are common contributors to plantar heel pain and must be noted and addressed for adequate long-term resolution of this problem. Ankle joint  equinus has been correlated with plantar fasciitis with an odds ratio of 23.3 for those with an ankle dorsiflexion less than 0 degrees.1 This lack of dorsiflexion at the ankle ultimately causes excessive subtalar pronation during gait as compensation, increasing the tensile load on the plantar fascia.9

Medial arch stability is largely dependent on the plantar ligaments, extrinsic muscles inserting on the first ray and the plantar fascia.10 Normally, the plantar fascia will act as a spring that can store energy and stabilize the medial column. Rush et al performed a cadaveric study investigating the role of the plantar fascia in medial column stability and determined that when there is insufficiency of the first ray, the windlass mechanism loses its effect, and the plantar fascia can no longer function as a stabilizer, leading to further deformity.11 However, with correction and restoration of the windlass mechanism, functional stability can be increased up to 26%. Medial column stability is largely dependent on the tension created by the windlass mechanism and the plantar fascia; without this physiological tension the medial arch becomes unstable, allowing subtalar overpronation and increasing plantar heel pain.12

A high-arched foot has also been associated with plantar heel pain due to increased tension on the plantar fascia. Golightly et al found that patients with an oversupinated foot were 1.51 times more likely to have plantar fasciitis.13 Similarly, patients with a flexible forefoot valgus deformity demonstrate an increased ground reaction force plantar to the first metatarsal head, allowing dorsiflexion of the medial column, increasing the origin-to-insertion distance of the plantar fascia with greater fascial tension, potential degeneration, and pain.

Similarly, overpronation of the subtalar joint with calcaneal eversion is a risk factor for plantar heel pain because of increased stretching of the plantar fascia. A meta-analysis determined there was moderate evidence that greater total rearfoot inversion/eversion motion existed in patients with plantar heel pain as compared with controls.14 Chang et al found that patients with plantar heel pain had increased rearfoot motion without a bias toward eversion or inversion.15 Studies have also demonstrated that a forefoot varus during the contact phase of gait had a greater range of pronation during stance, leading to increased plantar heel pain.16  Ankle equinus is also an important risk factor for plantar fasciitis. As noted earlier, a tight Achilles tendon with ankle dorsiflexion less than 0 degrees from neutral was found to have an odds ratio of 23.3 for plantar fasciitis.1 Additionally, a correlation was found between Achilles tendon loading and increased tension on the plantar fascia with a peak loading force in late stance phase.17 Johnson et al performed a cadaveric study to determine the influence of equinus on the first ray and medial column. They found that increasing the Achilles load had a dampening effect on the peroneus longus, thereby reducing its locking influence on the first ray and subsequent hypermobility.18 This hypermobility and medial arch instability increase plantar fascial tension in the manner described above.

Genu valgum may also contribute as an etiologic factor. Genu valgum is compensated by calcaneal eversion and subtalar pronation, increased plantar fascial tension, and heel pain.

Ankle joint equinus has been correlated with plantar fasciitis with an odds ratio of 23.3 for those with an ankle dorsiflexion less than 0 degrees.

The KK Approach to Treating Plantar Fasciitis

The kineticokinematic approach to plantar fasciitis guides treatment with a focus on decreasing plantar fascial strain via modification of the above-noted extrinsic and biomechanical factors. Currently available treatment options must then be understood for their kinetic and kinematic effects on the foot to decrease plantar heel pain.

Custom foot orthoses have been used to prevent or correct a deformity, promote a sound base of support, facilitate training in standing or walking, and improve the efficiency of walking.14 Orthoses also influence both kinetic and kinematic variables, including rearfoot eversion, tibial internal rotation, rearfoot eversion velocity, maximum ankle inversion moment, and maximum knee external rotation moment.19 In theory, a tissue accommodates to physical stress by adapting its own structure and composition to meet the mechanical demands of routine loading; but when the load exceeds what the tissue can accommodate,  injury occurs.20 Therefore, custom foot orthoses reduce stress on the injured tissue, allowing it to rest. An effective foot orthosis prescription should include modifications that will reduce the strain on the plantar fascia unique to the individual’s foot type and symptoms. Recommendations include a non-weightbearing cast of the foot to ensure the 1st ray is plantarflexed to the end of its range of motion, the posterior heel captured to allow frontal plane correction, and the plantar aspect represented precisely.21,22 A rearfoot varus extrinsic post and deep heel cup correct flexible calcaneal eversion,23 while a forefoot valgus wedge transfers loads to the lateral support structures, decreasing strain on the plantar fascia.24,25 Johanson et al also found the use of a 6–9 mm heel lift increased time to heel off,26 which is beneficial to decrease plantar fascial strain in patients with ankle equinus. Functional foot orthoses also alter the timing of forefoot loading during walking.27

The success of custom foot orthoses is variable in the literature. Scherer et al found orthoses increased 1st metatarsophalangeal joint dorsiflexion by 90%, effectively increasing the effect of the windlass mechanism,28 thus improving plantar fascia function. However, because an orthosis is created from static measures, it is assumed that the static position of the foot reflects the motion of the foot and ankle during ambulation, which is not necessarily true.29 The traditional purpose of casting to capture a “normally aligned foot” can be modified to instead target symptoms and the biomechanical cause of heel pain using a wide variety of orthosis modifications. Harradine et al recommended a narrow orthotic to decrease dorsiflexory moments of the 1st ray via kinetic wedges or first ray cutouts with inclusion of posting and a medial heel skive to increase the supinatory moments across the subtalar joint axis resulting in unloading stress from the plantar fascia.30

Other treatment options include prefabricated foot orthoses, which have been found in some studies to be nearly equal in clinical effect to custom foot orthotics and more cost effective.31 However, one must keep in mind the difficulty in adding long-lasting orthosis modifications to devices created to be temporary. Stretching exercises as a first-line treatment have been found to be effective when plantar fascia-specific stretches are incorporated, as opposed to isolated stretching of the Achilles tendon, which may result in greater reduction in pain, activity limitation, and patient satisfaction.32

Traditionally, plantar fasciitis was considered an injury caused by overuse leading to repetitive microtrauma and damage to the plantar fascia.4 Although the term “fasciitis” has been attributed to the diagnosis of heel pain originating from the plantar fascia, it implies an inflammatory process, but it may be more appropriately termed plantar fasciosis. Histological findings include collagen necrosis, angiofibroblastic hyperplasia, chondroid metaplasia, myxoid degeneration, and matrix calcification without leukocyte or macrophages, consistent with degenerative changes more so than an inflammatory process.1,2  Therefore, anti-inflammatory agents may be less useful, and treatment should instead target the root cause. Appreciating the chronic degenerative nature of this disorder leads one to reconsider currently common treatment methods such as corticosteroid injections. Kalaci et al found that patients receiving a corticosteroid injection with a peppering technique (multiple insertions of the needle into the plantar fascia) demonstrated a greater reduction in heel pain over 6 months than patients receiving cortisone alone, local anesthetic with peppering, or autologous blood.35 Peppering the fascia appears to introduce inflammatory cells, creating an acute condition, allowing healing and improved outcomes. More recently, platelet-rich plasma (PRP) injections have been used for chronic severe plantar fasciosis to introduce inflammatory cells to repair the damaged tissue. In a 2014 comparison of corticosteroid and PRP injections, Monto demonstrated effectiveness of both methods to improve American Orthopedic Foot and Ankle Society (AOFAS) scores initially. However, pain for those receiving steroid injections returned to baseline at 12 months post-treatment, while those receiving PRP injections showed improvement in functional scores past 24 months post-treatment.36

Increased BMI, another known risk factor, also falls under the KK treatment approach for plantar fasciitis. In a recent study, patients with a mean BMI of 45 and a history of plantar fasciitis underwent bariatric surgery resulting in an average BMI of 34.8. Nearly 90% of the patients studied achieved complete resolution of plantar fasciitis and related symptoms, indicating weight loss may be a highly effective part of the treatment for plantar fasciitis.37

Custom foot orthoses have been used to prevent or correct a deformity, promote a sound base of support, facilitate training in standing or walking, and improve the efficiency of walking.

Other interventions include shoe-gear changes and night splints. Batt and colleagues found significant improvement of plantar fasciitis symptoms in patients wearing night splints.38 Presumably, the effectiveness of night splints arises from a longer-term gastrocnemius stretch, counteracting some of the effect of ankle equinus.

In conclusion, the kineticokinematic approach may be applied to successfully treat plantar fasciitis by addressing the positional (kinematic) and dynamic (kinetic) forces that cause stress on the plantar fascia. With this novel approach, the goal is to improve patient function by focusing on the biomechanical etiologies and thereby reduce plantar heel pain.

Pedro Aldape-Esquivel, DPM, PGY-1, is a first-year resident at the Chino Valley Medical Center Podiatric Medicine and Surgery Program with Rearfoot Reconstruction and Ankle Certificate.

Jarrod Shapiro, DPM, FACPM, FACFAS, is an associate professor at the Western University of Health Sciences College of Podiatric Medicine and program director of the Chino Valley Medical Center Podiatric Medicine and Surgery residency. He is an active member of the American College of Foot & Ankle Orthopedics & Medicine (ACFAOM) and serves as its liaison on the LER Editorial Advisory Board.

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