Support for Using HeelRite™ Heel Seats for Infants with Overpronation: Part 2

Author: Beverly (Billi) Cusick, PT, MS, NDT, COF/BOC

SUBTALAR JOINT ANATOMY & FUNCTION
The calcaneus (heel bone) is the loading base of the hindfoot. The medial process of the posterior tuberosity contacts the ground.

The talus is the upper bone of the hindfoot. The talar body is boxed between the tibial and fibular malleoli like a mortise forming a mechanical connection between the talus and the leg bones in the frontal (mediolateral) and transverse (rotational) planes.

The calcaneus bears a projection on the upper inner surface known as the sustentaculum tali (ST) which means “sustains or supports the talus”. Using this projection, the calcaneus operates like a doorknob that can “open and close” the hindfoot. With the posterior calcaneus aligned in or near vertical position, the ST supports the medial talus. Calcaneal eversion – rotation of the tuberosity laterally – causes the ST to drop out from under the medial talus. Under bodyweight (BW), the unsupported talus falls forward and medially into the gap, and the “open” foot collapses into pronation, gaining momentary flexibility needed to soften the force of heel strike in gait. Inverting the calcaneus restores foot stability.

FLEXIBLE OVERPRONATION OR FLAT FOOT
Flexible flat foot is one of the most frequently cited concerns that prompt caregivers to seek the advice of physicians. [1] The common myth among most physicians - that “children outgrow foot pronation so we do not need to intervene” – is incorrect for 48.5% to 77.9% of children between the ages of 2 and 16 years [2,3,4] and 2% to 23% in adults.[5,6,7] Flexible pronation - a flattening of the midfoot under body weight that recovers when unloaded - ranges from ideal to pathomechanical in infants and children. The identification of overpronation is not made clear by researchers and currently seems to be relegated to those experienced clinicians who are trained to distinguish the pathomechanical foot features and related functional deficits from those that are not pathomechanical.

Most normative studies of developing musculoskeletal features include children who do not show evidence of brain injury or disease, and without excluding children who show overpronation, intoeing and out-toeing. The resulting normative databases embrace a wide range of differences in foot alignment. The dreaded “2 standard deviations” are applied to the means, expanding the boundaries of “normality” to exclude only the most severe of the study group. The criteria for those who are part of the “normative” group are poorly defined and the participants are not followed by researchers into early adulthood for long-term follow-up. We do not know whether children who reportedly showed less pronation at age 7 years than they did at age 4 years were fully corrected or still pronated enough to endure pathomechanical consequences later in life.

The classic sign of overpronation is visible heel eversion in standing position whereby the heel base is deviated outward and the foot joints remain static. The inner midfoot contacts the ground and is overloaded. The bodyweight follows the talus and falls forward toward the big toe. With weight displaced forward, the drive to stay upright triggers the toes to grasp the floor). With the medial foot pillars overloaded, the same drive triggers the toes to deviate laterally. Infants born prematurely and most with hypotonia do not have the frog-legged lower limb alignment of typical full-term newborns. With knees closer together, the BW falls either through - or medial to - the inner feet.

In my experience and that of Mary Weck, PT, the key concern in all cases of overpronation is the mechanical shift of BW forward and medial on the feet. Persistant forward BW cariage reduces heel loading, demanding chronic toe flexion and ankle plantarflexion for upright maintenance. Overpronation can precipitate the early onset of equinus deformity and toe walking.

Flexible flatfoot in adults almost always begins in childhood. Chronic overpronation changes limb joint alignment and BW carriage in daily life. If left unattended in early childhood, a cascade of muscle couple imbalances, joint degeneration, and pain can ensue in the second or third decades of life. The idea that intervention is warranted only when the condition is symptomatic pushes aside those young children who could avoid developing painful symptoms with preventative measures but have not yet developed symptoms seen later. Compared with older children and adults, the young child’s ligaments are less stiff, the bones are still ossifying, and the BW is low.

“Growing pains” are not a “normal” occurrence but are symptomatic of overpronation, featuring aching muscles, night cramps, or knee pain. Overpronation is often an element of functional shortfalls such as clumsiness, slower walking, frequent tripping, poor endurance, or aversion to sports that require running.[8]

The following potential long-term consequences of living in overpronation are cited by the Cleveland Clinic [9] and Molina-Garcia et al (2023): [10]

• Knee pain
• Hip pain
• Back pain
• Plantar fasciitis
• Bunions    
• Shin splints
• Achilles tendinitis
• Iliotibial band syndrome    
• Posterior tibial tendinopathy
• Hallux limitus and rigidus
• Chondromalacia patellae
• Patellofemoral pain syndrome 

I’ll add secondary equinus deformity as a factor in plantar fasciitis and Achilles tendonitis.

References
[1] Dars S, Uden H, Kumar S, Banwell HA. 2018. When, why and how foot orthoses (FOs) should be prescribed for children with flexible pes planus: a Delphi survey of podiatrists. Peer J. 6:e4667.
[2] Chen KC, Tung LC, Tung CH, et al. 2014. An investigation of the factors affecting flatfoot in children with delayed motor development. Res Developmental Disabilities. 35(3):639-45.
[3] Evans AM, Rome K. 2011. A review of the evidence for non-surgical interventions for flexible pediatric flat feet. Eur J Phys Rehabil Med. 47(1):1-21.
[4] Halabchi F, Mazaheri R, Mirshahi M, Abbasian L. 2013. Pediatric flexible flatfoot; clinical aspects and algorithmic approach. Iranian J Pediatrics. 23(3):247.
[5] Dunn JE, Link CL, Felson DT, et al. 2004. Prevalence of foot and ankle conditions in a multiethnic community sample of older adults. American J Epidemiology. 159(5):491-498.
[6] Golightly YM, Hannan MT, Dufour AB, Jordan JM. 2-12. Racial differences in foot disorders and foot type. Arthritis Care & Res. 64(11):1756-9.
[7] Kosashvili Y, Fridman T, Backstein D, Safir O, Ziv YB. 2008. The correlation between pes planus and anterior knee or intermittent low back pain. Foot & Ankle International. 29(9):910-913.
[8] D’Amico JC, Harris EJ. 2021. Pediatric Overpronation: Treat or Monitor? Podiatry Today. 25(12):
[9] Growing Pains in Kids: Causes & Symptoms. https://my.clevelandclinic.org/health/diseases/13019-growing-pains
[10] Molina-García C, Banwell G, Rodríguez-Blanque R, et al. 2023. Efficacy of plantar orthoses in paediatric flexible flatfoot: A five-year systematic review. Children.10(2):371.