Abstract
Background:
Pediatric flatfoot is a prevalent condition, and its assessment often involves clinical, radiographic, and functional measures. Although symptoms remain central to treatment decisions, radiographic angles, plantar-pressure metrics, and the Arch Index offer quantitative descriptors. Studying their interrelationships is useful to understand how structure and function are linked. This study examined plantar pressure distribution and the relationships among radiographic parameters, Arch Index, and dynamic loading.
Methods:
This retrospective single-center study included 27 children (51 feet) aged 10-18 years who were diagnosed with flexible flatfoot. Dynamic plantar pressure and contact area were measured, with foot segmentation guided by a foot axis defined as a straight line drawn from the midpoint between the second and third toes to the point of highest pressure in the heel region. Weight-bearing radiographs were used to assess the Meary angle and calcaneal pitch. The Arch Index was derived from dynamic footprints. Correlations among plantar pressure ratios, Arch Index, and radiographic angles were analyzed.
Results:
Radiographic assessment confirmed flatfoot deformity (mean Meary angle, 20.07°; calcaneal pitch, 11.75°) and an elevated Arch Index. Forefoot loading showed significant anteromedial predominance (medial pressure ≈1.5 × lateral, P < .01), whereas no mediolateral differences were observed in the midfoot or hindfoot. Correlation analysis revealed no significant relationships among the plantar pressure ratio, Arch Index, and radiographic measurements.
Conclusion:
In adolescent flexible flatfoot, dynamic loading demonstrates anteromedial forefoot predominance. Radiographic angles and dynamic (pedobarography) assessments capture complementary, non-interchangeable aspects of flatfoot. Dynamic analysis may provide additional insight into region-specific loading patterns. Further studies are needed to define its role in clinical decision making.
Level of Evidence:
Level III, diagnostic, retrospective.
Introduction
Flatfoot, characterized by the collapse or flattening of the medial longitudinal arch, is one of the most prevalent foot posture abnormalities in the pediatric population. 1 Approximately 90% of the clinical appointments for foot-related issues among school students are attributed to flatfoot. 2
All infants are born with flatfoot, and the longitudinal arch of the foot develops during the first decade. 3 The prevalence of flatfoot is 37% to 59.7% in children aged 2-6 years and 4% to 19.1% in those aged 8-13 years.3 -5 Evaluating children with a flatfoot posture is important to determine whether treatment is needed to prevent future complications, such as pain, joint deformity, or gait instability.6 -8
The foot plays a vital role in absorbing impact, transmitting ground reaction forces, and maintaining balance during ambulation. 9 Structural abnormalities of the foot can result in inefficient gait patterns and altered biomechanical function, leading to increased use of pressure assessment methods. 10
Traditionally, diagnosis and monitoring rely heavily on static clinical assessments supplemented by radiographic measurements, most commonly Meary angle and calcaneal pitch, which provide estimates of bone alignment and arch integrity.11,12 However, these radiographic parameters may not accurately reflect functional foot biomechanics during gait.10,13
Dynamic plantar pressure analysis provides quantitative assessment of regional load distribution during walking and reflects both structural and functional characteristics of the lower extremity.14 -16 It has been shown to be a reliable method for evaluating foot function, 17 offering clinicians valuable insights for determining optimal treatment approaches.
Although clinical symptoms remain the primary determinant for intervention in pediatric flatfoot, objective measures such as radiographic angles, plantar pressure distribution, and the Arch Index provide reproducible quantitative data. Understanding the relationships among these parameters may clarify how structural alignment relates to functional loading and whether these modalities offer complementary or redundant information.
Therefore, this study aimed to characterize regional plantar contact distribution and to evaluate the relationships among plantar pressure patterns, radiographic parameters, and the Arch Index in adolescents with flexible flatfoot.
Materials and Methods
Study Design and Participants
This retrospective, single-center observational study was conducted to evaluate the plantar pressure distribution and radiographic parameters in children diagnosed with flexible flatfoot. Medical records of patients who visited the foot clinic between 2021 and 2025 were reviewed. Twenty-seven children (23 males and 4 females) with 51 affected feet met the inclusion criteria and were enrolled in the study. Data on demographic characteristics, including age, sex, height, weight, and body mass index, were obtained.
Inclusion and Exclusion Criteria
The inclusion criteria were as follows: (1) age between 10 and 18 years; (2) clinical diagnosis of flexible flatfoot, defined as the presence of a collapsed medial longitudinal arch during weight-bearing with reconstitution of the arch during non-weight-bearing or heel-raising; and (3) presence of symptoms attributable to flatfoot, including 1 or more of the following: pain in the medial arch, heel, or ankle; fatigue or discomfort after physical activity; functional limitation during sports or daily activities; or abnormal shoe wear related to flatfoot.
The exclusion criteria were as follows: (1) rigid flatfoot, (2) previous lower limb surgery or trauma, (3) neuromuscular disorders, (4) central nervous system pathology, and (5) congenital foot deformities. Informed consent was obtained from the parents or guardians of all participants, and the study design was exempt from ethical review in accordance with the institutional policies.
Plantar Pressure Measurement
Figures 1 and 2 show dynamic plantar pressure data collected using GaitView Pro 1.0, a pedobarographic platform with embedded capacitive sensors (Alfoots Co, Korea). Participants were instructed to walk barefoot at a self-selected pace along a 10-m walkway. Pressure data were recorded at a sampling frequency of 60 Hz for both feet. Each foot was assessed 3 times, and the average values were used for the analysis. The plantar surface of the foot was divided into anatomic regions: toes, metatarsals, midfoot, and heel. For each region, plantar pressure (kPa) and contact area (cm²) were measured.
Illustration of regional plantar pressure distribution.
Plantar foot pressure mapping.
For regional analysis, the plantar surface of the foot was segmented, primarily by defining the foot axis as a straight line drawn from the midpoint between the second and third toes to the point of highest pressure identified in the heel. This axis guided the medial and lateral division of the foot for comparative analysis.
Radiographic Assessment
Standardized weight-bearing anteroposterior and lateral radiographs of both feet were obtained. Two radiographic parameters were measured: Meary angle (lateral talo-first metatarsal angle) and calcaneal pitch angle (Figure 3). All radiographic measurements were performed by a single orthopaedic surgeon with experience in flatfoot assessment and were independently reviewed by a second clinician for verification; however, interrater reliability was not assessed and is acknowledged as a limitation of the study.
Foot radiograph showing (A) Meary angle and (B) calcaneal pitch. 18
Arch Index Calculation
The Arch Index was calculated from footprint data obtained during dynamic pedobarography trials as the ratio of the midfoot contact area to that of the entire foot, excluding the toes.
Statistical Analysis
All analyses were performed using SPSS Statistics software version 22.0 (IBM, Armonk, NY). Mean ± SD and range were used for continuous variables, whereas frequencies and percentages were used for categorical variables. Medial-to-lateral plantar pressure ratios were compared across foot regions using paired t tests or Wilcoxon signed-rank tests, depending on the data distribution (normality was assessed using the Shapiro-Wilk test). Correlation analyses were performed to examine the relationships among plantar pressure ratios (M1/L1, M2/L2, and M3/L3), the Arch Index, and radiographic parameters (Meary angle and calcaneal pitch). Medial-to-lateral plantar pressure ratios were calculated for each anatomical region: M1:L1 (toes), M2:L2 (forefoot), and M3:L3 (midfoot), defined as the ratio of mean plantar pressure in the medial compartment to that in the lateral compartment.
In normal foot alignment, these ratios are expected to approximate 1, indicating balanced load distribution. In contrast, flatfoot deformity is hypothesized to increase medial loading, resulting in ratios greater than 1, particularly in the anterior foot.
Pearson correlation coefficients were used for parametric data, whereas Spearman rank correlation was applied for nonparametric variables. P value <.05 was considered statistically significant.
Missing data
Three feet with incomplete plantar-pressure recordings and/or inconsistent radiographic measurements were excluded listwise from affected analyses; no imputation was performed.
Power considerations
Post hoc calculations indicated that with a sample of 51 feet, the study had ~80% power to detect correlations of |r|≈0.38 (test of ρ = 0 at α = 0.05); smaller associations may not have been detectable.
Results
Patient Demographics
We obtained plantar pressure data from 51 feet of 27 individuals for analysis. The mean age of the participants was 13.43 ± 1.68 years (range: 10-18 years), and 23 were male. The mean body mass index was 21.35 ± 2.58 (Table 1). Three feet were excluded because of incomplete plantar pressure recordings or inadequate radiographic data. Incomplete recordings were related to technical factors such as partial foot contact, whereas inadequate radiographic measurements were due to suboptimal positioning, including missing standardized weight-bearing views.
Demographic Characteristics of Study Participants.
Abbreviation: BMI, body mass index.
Plantar Contact Area Ratios
Analysis of medial-to-lateral plantar contact area ratios revealed distinct regional patterns (Table 2). In the midfoot and hindfoot regions, the medial and lateral contact areas were approximately equal, with mean medial/lateral ratios of 1.02 ± 0.44 (P = .73) and 1.00 ± 0.18 (P = .88), respectively. In contrast, the forefoot region demonstrated a notable asymmetry, where the medial contact area was approximately 1.4 times larger than the lateral contact area (mean ratio 1.40 ± 0.12, P = .006).
Plantar Contact Area Medial to Lateral Ratio.
Plantar Pressure Distribution
Bilateral data were analyzed to explore within-subject variability in plantar pressure distribution. One foot was not considered a normal control for the other, and side-to-side comparisons were interpreted descriptively. Medial-to-lateral plantar pressure distribution also varied by foot region (Table 3). In the forefoot, medial plantar pressure was significantly higher than lateral plantar pressure for both the right (9.12 ± 2.10 N/cm2 vs 6.43 ± 1.93 N/cm2, P = .001) and the left (8.67 ± 2.71 N/cm2 vs 6.06 ± 1.68 N/cm2, P = .003) feet. Conversely, no significant difference in plantar pressure was observed between the medial and lateral aspects of the hindfoot.
Plantar Pressure Measurement per Contact Area.
Further analysis of medial-to-lateral plantar pressure ratios (Table 4) indicated a predominance of medial pressure in the anterior foot, with ratios of approximately 2.7 in the toe region and 1.5 in the forefoot. We report these ratios primarily as descriptive indices to complement the paired tests above.
Mean Values for the Plantar Pressure Ratio, Radiographic Angles, and the Arch Index.
Radiographic Parameters and the Arch Index
Radiographic assessments confirmed the presence of flatfoot deformity in the study cohort. The mean Meary angle was 20.07 ± 6.13 degrees, indicating plantarflexion of the talus relative to the first metatarsal. The mean calcaneal inclination angle was 11.75 ± 4.51 degrees, reflecting decreased calcaneal pitch characteristic of flatfoot. The Arch Index was also elevated, consistent with increased midfoot contact area typical of flatfoot deformities. (Table 4)
Correlation Analysis
We estimated correlations among the regional medial-to-lateral pressure ratios (M1/L1, M2/L2, M3/L3), the Arch Index, and the 2 radiographic measures (Meary angle and calcaneal inclination angle) using Pearson correlation matrix. A moderate positive correlation was observed between the midfoot medial-to-lateral pressure ratio (M3:L3) and the Arch Index, whereas no significant correlations were found between plantar pressure ratios and the radiographic angles. Given our sample size (n = 51 feet), post hoc calculations indicate ~80% power to detect correlations of |r|≈0.38 or larger; however, this estimate assumes independence of observations. Because bilateral feet from the same participant were included, the P values and power estimates should be interpreted with caution, as the effective sample size may be smaller than the nominal number of feet (Table 5).
Correlation Analysis Results.
Discussion
This study was conducted to assess plantar pressure distribution and radiographic parameters, and to investigate the relationship among plantar pressure patterns, the Arch Index, and radiographic measurements in adolescents with flexible flatfoot. Given the limited prior work integrating these modalities in this population, our goal was descriptive—to clarify what each measure captures—rather than to define clinical severity or predict outcomes.
Radiographic parameters such as Meary angle and calcaneal pitch primarily reflect sagittal alignment and structural configuration of the medial longitudinal arch under static weight-bearing conditions. The Arch Index quantifies the relative contact area of the midfoot and serves as an indirect indicator of arch collapse.
In contrast, dynamic plantar pressure analysis reflects functional load distribution during gait, integrating not only skeletal alignment but also soft-tissue behavior, neuromuscular control, and temporal loading patterns. As such, pedobarography provides information on where and how forces are applied across the foot, which cannot be inferred from static measurements alone.
Understanding these differences is essential for clinical interpretation. Rather than being interchangeable, these parameters describe distinct aspects of foot function and structure, and their combined use may provide a more comprehensive assessment of flexible flatfoot.
The radiographic parameters from our cohort confirmed the presence of flatfoot deformity, consistent with the findings of a previous study. 19 The elevated Arch Index observed in our study corroborates these findings, signifying increased contact area in the midfoot region, which is consistent with arch collapse. 20
Anatomically and biomechanically, arch collapse in flexible flatfoot occurs predominantly at the medial midfoot. Accordingly, our a priori hypothesis was that medial pressure would exceed lateral pressure in the midfoot. However, the result showed no statistically significant medial-lateral difference at the midfoot (ratio ≈ 1.0), whereas loading concentrated in the forefoot with a clear medial predominance there. Lee et al 21 also reported a higher medial-to-lateral pressure ratio in pediatric flatfoot, with medial pressure being 1.63 times greater than lateral pressure in the forefoot, a finding comparable to ours.
No statistically significant correlations were found among key radiographic measurements (Meary angle and calcaneal angle), the Arch Index, and plantar pressure parameters, consistent with prior findings.21,22 Given our achieved sample, the study was powered to detect moderate correlations but may have missed small effects. Radiographs and the Arch Index primarily reflect sagittal/postural configuration under static conditions, whereas pedobarography integrates multiplanar kinematics, soft tissue compliance, and neuromuscular control during gait; a tight correspondence between these domains is therefore not theoretically required. Moreover, in children, flatfoot is often due to the elasticity of the subtalar joint ligament complex, which may not significantly affect the main pressure-bearing areas of the foot. This lack of a direct impact on major pressure points may explain why wearing corrective footwear for asymptomatic physiological flatfoot is often considered unnecessary.
It is important to highlight the methodological differences and enhancements in our study. Lee et al 21 segmented the foot into toe, forefoot, and hindfoot regions, whereas we further included the midfoot region (the site of arch collapse) and hypothesized increased medial midfoot pressure compared with the lateral side. Moreover, our foot segmentation method, based on a functional foot axis defined from the point of highest pressure in the heel region (an area where pressure is typically unaffected by flatfoot), is considered more optimal than prior methods that rely on fixed anatomical landmarks. Furthermore, we used average pressure over contact area, instead of peak or total pressure, based on the belief that, in children, pressure variation is primarily influenced by contact area size and bony landmarks. Consequently, average pressure in the functional region provides the best reflection of the overall pressure distribution.
We also specifically evaluated the Arch Index (the ratio of the middle third of a footprint to the total footprint area) to determine its correlation with plantar pressure. Angular measurements on radiographs indirectly reflect the degree of foot flattening and are based on 2D images, whereas the Arch Index directly reflects the contact area of the sole with the ground, which theoretically influences plantar pressure changes. Despite this, our results extend prior findings by showing no significant linear relationship between the Arch Index and regional plantar pressure ratio.
Clinical decision making in pediatric flatfoot is multifactorial and depends on both clinical and structural factors. One of the key distinguishing features is deformity flexibility, as rigid flatfoot is more often associated with underlying pathology and may warrant different management compared with flexible deformity. 23
Although pediatric flexible flatfoot is frequently asymptomatic, a subset of patients present with activity-related pain, fatigue, and functional limitation. Importantly, the decision to initiate treatment is primarily symptom-driven rather than based solely on structural parameters.
First-line management remains nonoperative, including activity modification, orthotic intervention, and structured rehabilitation. Operative treatment is generally considered only in cases of persistent symptoms, progressive deformity, or severe functional impairment despite appropriate conservative measures.
A limitation of our study is its small sample size, a common challenge in biomechanical research on flexible flatfoot. Correlation analyses were performed without accounting for within-subject clustering of bilateral observations. As a result, the assumption of independence may have been violated, potentially leading to underestimation of standard errors and more liberal P values, as well as overestimation of statistical power. Therefore, correlation findings should be interpreted with caution. Age-related variation in arch development and plantar pressure distribution may act as a confounding factor. Although the cohort was restricted to adolescents (10-18 years), age was not included as an independent variable or adjusted for in the analysis, which may influence the observed relationships. Additionally, the study cohort was predominantly male (23 of 27 participants), which may limit generalizability to female patients and does not reflect the broader sex distribution of pediatric flexible flatfoot. Future studies with larger sample sizes and subgroup analyses are required to eliminate confounding factors that may affect plantar pressure, specifically radiographic severity.
Conclusions
In adolescent flexible flatfoot, dynamic loading demonstrates anteromedial forefoot predominance and is not significantly correlated with radiographic parameters or the Arch Index. These findings suggest that radiographic angles and dynamic (pedobarography) assessments capture complementary, noninterchangeable aspects of foot structure and function.
Dynamic plantar pressure analysis provides additional insight into regional loading patterns; however, its role in guiding clinical decision making requires further investigation.
Supplemental Material
sj-pdf-1-fao-10.1177_24730114261450616 – Supplemental material for Adolescent Flexible Flatfoot: A Cross-Sectional Analysis of Radiographs, Arch Index, and Plantar Pressure
Supplemental material, sj-pdf-1-fao-10.1177_24730114261450616 for Adolescent Flexible Flatfoot: A Cross-Sectional Analysis of Radiographs, Arch Index, and Plantar Pressure by Ngoc Minh Ho, Duc Huy Le, Van Thanh Nam Ta, Huu Phuc Luu, Nhat Anh Luong, Duc Trung Nguyen, Ba Quynh Phan, Duc Thang Vu, Tu Nam Vu and Trung Dung Tran in Foot & Ankle Orthopaedics
Footnotes
Acknowledgements
Ethical Considerations
This study was conducted using retrospective data and was exempt from ethical review in accordance with the institutional policies of Vinmec International Hospital. All data were anonymized prior to analysis, and the study complied with the principles outlined in the Declaration of Helsinki.
Consent to Participate
Informed consent was obtained from the parents or guardians of all participants.
Consent to Publication
Not applicable.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosure forms for all authors are available online.
Data Availability Statement
The data set used in our study are available from corresponding author upon reasonable request.
References
Supplementary Material
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