The proposed association between obesity and pediatric flexible flatfoot (PFF) may depend more on the reliance on subjective, 2D footprint-based assessments than true correlation. And recent research has identified another potential risk factor, whole body and joint hypermobility.
By Hank Black
As accumulating evidence continues to suggest the proposed association between obesity and pediatric PFF is largely the product of unsophisticated arch height assessment methods, a leading researcher in the area is calling clinicians’ attention to a different risk factor.
Podiatrist Angela M. Evans, PhD, who has spent years analyzing factors that may be associated with PFF, recently issued a wake-up call for practitioners to have a heightened suspicion that children with flatter feet than expected for their age may have whole body or lower limb joint hypermobility.
“Most astute clinicians already are aware of this possibility,” said Evans, who has a podiatry practice in Adelaide, Australia, and holds a research position at La Trobe University in Melbourne.
In a 2016 study published in the Journal of Foot & Ankle Research,1 Evans and colleagues looked at the relationship between foot posture and body mass index (BMI), age, and ankle, lower limb, and whole body flexibility in a convenience sample of 30 healthy children aged 7 to 15 years. Clinical data assessed included BMI, Foot Posture Index (FPI), Beighton scale score,2 lower limb assessment scale score (LLAS),3 and left ankle lunge angle.
The group found no association between PFF and BMI, age, or gender. Interestingly, however, they found that PFF was associated with joint and whole body flexibility.
Given that hypermobility can be associated with morbidity that may persist across the lifespan,4 the condition “is too often disregarded as being benign or even advantageous,”5 the authors wrote.
“Whilst a small study, the findings are notable,” Evans said. “We need to look in quite a structured way at why these children are maintaining flatfoot. Is there an underlying neurological issue? Is there an issue with muscular function or structure? Is there an unrecognized genetic issue, such as Marfan syndrome or Ehlers-Danlos syndrome? Maybe a difference in connective tissue?”
Of particular interest, she said, are children with hypermobile joints that exceed “childhood flexibility,” and continue at an older age than when developmental flatfoot is expected.
“It’s very important to question why could this be, and look further, because hypermobility is not always just more flexible joints,” Evans said. “Some types of Ehlers-Danlos syndrome, for example, can have significant underlying cardiac and ocular conditions that can threaten the child’s health and life. So we need to be mindful that sometimes PFF, when not usual for age, might be the start of a thread that discloses more about a child’s overall health.”
Associations between PFF and hypermobility have been previously reported in the literature6,7 and are commonly observed clinically. But the complexities of hypermobility warrant closer investigation of these relationships, Evans said.
“Hypermobility may be specific to that child or it may be a familial pattern in first-degree relatives,” she said. “Then again, we may be looking at hypermobility that is present and reducing with age. That may also be accompanied by muscular hypotonia, which, if not condition-associated, also often reduces with age, but may delay motor development.” (see “Gait: The cornerstone of intervention,” In Step with Pediatric Hypotonia, September 2013, page 8.)
Management of generalized hypermobility has not been well studied, particularly in children, but tends to focus on improving posture, joint stability, and specific motor skills; protocols often include pain-free cognitive exercises to enhance proprioception and muscle strength.8-11 The lack of evidence has made developing effective lower extremity interventions a challenge.
“Certainly benign joint hypermobility is well known since Beighton developed the concept years ago.12 The question is how to manage it,” said foot and ankle surgeon Gregory Guyton, MD, who practices at MedStar Union Memorial Hospital in Baltimore, MD. “Unfortunately, there’s nothing you can do to truly tighten the plantar ligaments on the medial side of the foot if indeed they have ligament laxity. There are no exercises that would make any real difference.”
Christopher L. Reeves, DPM, who practices at the Orlando Foot and Ankle Clinic in Orlando, FL, said he and his colleagues have had success with orthotic management of symptomatic PFF in young children with hypermobility.
“Our conservative management of hypermobility might be an aggressive L-type orthosis,” Reeves said. “In a foot that’s really hypermobile and symptomatic, I’ll use a UCBL [University of California Biomechanics Laboratory] type. I find this works extremely well in younger kids, who tolerate it very well. Once they get to ten or twelve years old, especially if they have no previous experience with an orthosis, they find it too aggressive.”
Reeves believes a stretching program helps in children with tightness in posterior muscles from the Achilles to the gastrocnemius complex.
“That’s especially found in larger kids whose soft tissue structures don’t always keep up with bone growth. Sometimes stretching allows kids to better tolerate their activity level overall,” he said.
Although posterior muscle tightness may seem to suggest hypomobility, not the opposite, Reeves said he doesn’t correlate the two. “One can have a hypermobile flexible flat foot [joint laxity] yet have tight soft tissue structures [tendons] about the ankle,” he said. “I find that children with flat feet are tight in the gastrocsoleus complex, as well as in the hamstrings, and think an overall stretching program can be beneficial in the long run.”
Surgical intervention in children with PFF is typically reserved for severe cases that have not responded to other treatments, but for these children, hypermobility can also complicate surgical efforts.
“If you have a case involving global ligamentous laxity, you can’t really trust any reconstructions you do with that patient’s own ligaments. So, if you have joint instability that requires a fusion, you’re much better off relying on their bones than their ligaments,” Guyton said.
Hypermobility can turn a straightforward surgical procedure into something more complex, Reeves noted.
“It depends on the patient, but in a simple case, I’ll perform a realignment calcaneal hindfoot osteotomy,” Reeves said. “Occasionally we’ll also do a medial foot soft-tissue reconstruction because, after you’ve realigned the foot, there’s a lot of laxity that needs to be addressed where that site’s been stretched out.”
The obesity question and PFF assessment
In the 2016 study by Evans et al, the lack of association between BMI and PFF is consistent with previous studies by the same research group13,14 and contrasts with the findings of multiple other studies that used a different method of defining PFF.
It once seemed intuitive that overweight children are more likely than normal-weight children to have flat feet, and many studies have reached that conclusion.15-21 Most of those studies, however, used a variety of at least partially subjective measures of foot morphology based on printed, scanned, or digitized footprints.
Evans’s studies, in contrast, used the six-item FPI, which accounts for the 3D nature of foot posture and achieves good reliability in adults22,23 and children.22,24-26
The six criteria used include: (1) talar head palpation; (2) curves above and below the lateral malleolus; (3) inversion/eversion of the calcaneus; (4) bulge in the region of the talonavicular joint; (5) congruence of the medial longitudinal arch; and (6) abduction/adduction of the forefoot on the rearfoot.
Each criterion was given a score between -2 and +2, for which scores less than zero indicate a supinated alignment and scores greater than zero indicate a pronated alignment. Scores of all criteria were added to create an overall score for each foot from -12 (most supinated) to +12 (most pronated). The mean FPI score for the study population in Evans et al’s 2016 paper was 2.8 ± 2.3.
“FPI is now seen as a repeatable, reliable measure with some levels of validation, and it is being increasingly used in a number of subjects, including some involving pediatric populations. It’s relatively quick and simple to use,” Evans said.
Clinically, however, FPI isn’t yet universally accepted.
“FPI is a great research tool, although I don’t know of anyone using it in general clinical practice,” Evans said. “For me, it’s all clinical evaluation, a visual analysis of gait, and a family history, with radiographs playing a huge role.”
Guyton said he has used FPI for clinical screening.
“It has been validated against radiographs, and we use radiographs when we are assessing patients preoperatively,” he said.
Amber Shane, DPM, a colleague of Reeves at the Orlando Foot and Ankle Clinic, also evaluates with x-rays and, to make sure the arch is flexible, the heel-rise test.27
“With flatfoot, you’re going to see where the talus and the navicular that normally articulate about seventy five percent, you’re going to see less than fifty percent,” Shane said.
Evans said recent research is giving a clearer picture about the evaluation and classification of PFF. A 2016 report from Spanish researchers28 used the FPI and, like Evans and colleagues, found no association between obesity and flatfoot. The same group also determined normative FPI values for children, though the participants’ age range was limited to 6 to 11 years, and they were not overweight (average BMI 16.9). These normative data could be used to help clinicians identify children who need to be referred elsewhere for deeper analysis of gait or growth, and also to help monitor changes in physiological or pathological foot posture during childhood, the authors noted.
The predominance of footprint-based measures of flat feet in the PFF literature was clear in a 2015 systematic literature review by Stolzman et al that included studies through 2013.29 The researchers analyzed 13 cross-sectional studies of varied designs. None used the FPI; most used a footprint-based measure, clinical examination, or other methods requiring some degree of subjectivity. Due to the few studies published that met study criteria, different methodologies used, lack of definition of pes planus, and few studies of pain and other potential complications, the authors of the review called for more research to determine the relationships between body weight, pes planus, and associated pain and function effects.
Stolzman et al did not include Evans’s seminal 2011 study of 140 Australian schoolchildren, which utilized FPI to determine there was not a direct relationship between increased body mass and flatter feet.13 That study was expanded and its results confirmed in a 2015 publication involving 728 children.14 In it, Evans reviewed 11 studies from 2001 to 2013; her 2011 study13 was the only one that did not find a significant relationship between foot posture and body mass.
Evans’ current work includes preparing an update to the 2010 Cochrane Review she coauthored on nonsurgical interventions for PFF.30 She has also has launched a new pediatric podiatry resource, Evidence Essentials, online at her website, angelaevanspodiatrists .com.au.
Even in the absence of a statistical association between BMI and PFF, both Reeves and Guyton noted symptoms associated with PFF can be exacerbated when kids become obese.
“Children who otherwise would manage with flat feet will get larger and suddenly the flatfoot becomes symptomatic,” Guyton said. “The force on the arch is greater, or sometimes flatfoot becomes symptomatic because of lateral impingement with the arch collapses to the degree that the calcaneus impinges against the tip of the fibula.”
Evans’ proposal to use FPI instead of footprints to help diagnose pediatric flexible flatfoot wasn’t her first run-in with a legacy practice. In a 2008 paper31 Evans stirred up some practitioners by recommending that asymptomatic children whose feet are flatter than would be expected for their age group should not be automatically treated (with customized orthoses).
Her thesis to monitor or “address the basics” (footwear, strengthening, stretching) was based on studies32-34 conducted as early as 1989 that showed no structural foot change in normal-weight children over a number of years versus controls.
“With the renaissance of evidence-based medicine, it behooves us as clinicians to be more scientific and informed about our approach,” she told LER in 2010 (See “Numbers needed to treat? The pediatric flexible flatfoot debate,” January 2010, page 22).
Guyton said he’s seen no evidence for the prophylactic use of orthoses in kids with PFF who do not have symptoms.
“If the youngster has no symptoms and no secondary issues such as the ankle tilting, then the right answer is to do nothing,” he said. “If the flatfoot becomes painful then we will usually try orthotics.”
Reeves doesn’t discount the use of orthoses even for asymptomatic patients.
“If the flatfoot is severe and asymptomatic, and the child can tolerate orthotic therapy well, I’ll at least recommend orthoses if they feel better and their shoe fits better,” he said.
Shane noted that symptoms can be more than just pain.
“Children with flexible flatfoot may tire before other children do, perhaps tripping or falling, [moving] slower on the athletic field, and feel clumsy in their shoes,” she said.
Hank Black is a freelance writer in Birmingham, AL.
- Hawke F, Rome K, Evans AM. The relationship between foot posture, body mass, age and ankle, lower-limb and whole-body flexibility in healthy children aged 7 to 15 years. J Foot Ankle Res 2016;9:14.
- Van der Giessen LJ, Liekens D, Rutgers KJ, et al. Validation of Beighton score and prevalence of connective tissue signs in 773 Dutch children. J Rheumatol 2001;28(12):2726-2730.
- Ferrari J, Parslow C, Lim E, et al. Joint hypermobility: the use of a new assessment tool to measure lower limb hypermobility. Clin Exp Rheumatol 2005;23(3):413-420.
- Tofts LJ, Elliott EJ, Munns C, et al. The differential diagnosis of children with joint hypermobility: a review of the literature. Pediatr Rheumatol 2009;7:1.
- O’Sullivan P, Beales D, Jensen L, et al. Characteristics of chronic non-specific musculoskeletal pain in children and adolescents attending a rheumatology outpatients clinic: a cross-sectional study. Pediatr Rheumatol Online J 2011;9:3.
- El O, Akcali O, Kosay C, et al. Flexible flatfoot and related factors in primary school children: a report of a screening study. Rheumatol Int 2006;26(11):1050-1053.
- Lin CJ, Lai KA, Kuan TS, Chou YL. Correlating factors and clinical significance of flexible flatfoot in preschool children. J Pediatr Orthop 2001;21(3):378-382.
- Kerr A, Macmillan CE, Uttley WS, Luqmani RA. Physiotherapy for children with hypermobility syndrome. Physiotherapy 2000;86(6):313-317.
- Simmonds JV, Keer RJ. Hypermobility and the hypermobility syndrome, Part 2: assessment and management of hypermobility syndrome: illustrated via case studies. Manual Therapy 2008;13(2):e1–e11.
- Keer R, Simmonds J. Joint protection and physical rehabilitation of the adult with hypermobility syndrome. Current Opinion in Rheumatology 2011;23(2):131-136.
- Scheper MC, Engelbert RH, Rameckers EA, et al. Children with generalised joint hypermobility and musculoskeletal complaints: state of the art on diagnostics, clinical characteristics, and treatment. Biomed Res Int 2013;2013:121054.
- Beighton PH, Solomon L, Soskolne CL. Articular mobility in an African population. Ann Rheum Dis 1973;32(5):413-418.
- Evans AM. The pediatric flat foot and general anthropometry in 140 Australian school children aged 7–10 years. J Foot Ankle Res 2011;4:12.
- Evans AM, Karimi L. The relationship between pediatric foot posture and body mass index: do heavier children really have flatter feet? J Foot Ankle Res 2015;8:46.
- Pfeiffer M, Kotz R, Ledl T, et al. Prevalence of flat foot in preschool-aged children. Pediatrics 2006;118(2):634–639.
- Villarroya MA, Esquivel JM, Tomás C, et al. Assessment of the medial longitudinal arch in children and adolescents with obesity: footprints and radiographic study. Eur J Pediatr 2009;168(5):559-567.
- Chen JP, Chung MJ, Wang MJ. Flatfoot prevalence and foot dimensions of 5- to 13-year-old children in Taiwan. Foot Ankle Int 2009;30(4):326-332.
- Chang JH, Wang SH, Kuo CL, et al. Prevalence of flexible flatfoot in Taiwanese school-aged children in relation to obesity, gender, and age. Eur J Pediatr 2010;169(4):447-452.
- Mauch M, Grau S, Krauss I, et al. Foot morphology of normal, underweight and overweight children. Int J Obes (Lond) 2008;32(7):1068-1075.
- Morrison SC, Durward BR, Watt GF, Donaldson MDC. Prediction of anthropometric foot characteristics in children. J Am Podiatr Med Assoc 2009;99(6):497-502.
- Woźniacka R, Bac A, Matusik S, et al. Body weight and the medial longitudinal foot arch: high-arched foot, a hidden problem? Eur J Pediatr 2013;172(5):683-691.
- Redmond AC, Crosbie J, Ouvrier RA. Development and validation of a novel rating system for scoring standing foot posture: the Foot Posture Index. Clin Biomech 2006;21(1):89-98.
- Redmond AC, Crane YZ, Menz HB. Normative values for the Foot Posture Index. J Foot Ankle Res 2008;1(1):6.
- Lee JS, Kim KB, Jeong JO, et al. Correlation of foot posture index with plantar pressure and radiographic measurements in pediatric flatfoot. Ann Rehabil Med 2015;39(1):10-17.
- Morrison SC, Ferrari J. Inter-rater reliability of the Foot Posture Index (FPI-6) in the assessment of the paediatric foot. J Foot Ankle Res 2009;2:26.
- García-Rodríguez A, Martín-Jiménez F, Carnero-Varo M, et al. Flexible flat feet in children: a real problem? Pediatrics 1999;103(6):e84.
- Yocum A, McCoy SW, Bjornson KF, et al. Reliability and validity of the standing heel-rise test. Phys Occup Ther Pediatr 2010;30(3):190-204.
- Gijon-Noqueron G, Montes-Alquacil J, Alfageme-Garcia P, et al. Establishing normative foot posture index values for the pediatric population: a cross-sectional study. J Foot Ankle Res 2016;9:24.
- Stolzman S, Irby MB, Callahan AB, et al. Pes planus and pediatric obesity: a systematic review of the literature. Clin Obes 2015;5(2):52-59.
- Rome K, Ashford RL, Evans A. Non-surgical interventions for paediatric pes planus.Cochrane Database Syst Rev 2010:CD006311.
- Evans AM. The flat-footed child—to treat or not to treat: what is the clinician to do? J Am Podiatr Med Assoc 2008;98(5):386-393.
- Wenger DR, Maudlin D, Speck G, et al. Corrective shoes and inserts as treatment for flexible flatfoot in infants and children. J Bone Joint Surg Am 1989;71(6):800-810.
- Powell M, Seid M, Szer IS. Efficacy of custom foot orthoses in improving pain and functional status in children with juvenile idiopathic arthritis. J Rheumat 2005;32(5):943-950.
- Whitford D, Esterman A. A randomized controlled trial of two types of 9n-shoe orthoses in children with flexible excess pronation of the feet. Foot Ankle Int 2007;28(6):715-723.