Foot types differ according to foot shape and foot arch height. Flatfoot and cavus foot are common but complex foot deformities. The flatfoot deformity is characterized by a combination of a collapse of the medial longitudinal arch, foot abduction at the talonavicular joint, and hindfoot valgus [12]. The cavus foot deformity is the opposite. Either deformity may be a predisposing factor for injuries in the lower extremity [345].

In Korea, the concept of foot deformity is especially well-known in the general population, especially flatfoot. Much of the recognition is because flatfoot is an important physical examination feature for military qualification in South Korea. The qualification examination for the Korean military includes plantar measurement, since flatfoot may result in various podiatric symptoms or functional impairment in soldiers who are already prone to pain or injuries in lower extremities due to excessive marching or weight-bearing activities.

While the concept of this disorder is widely familiar, the diagnosis of this condition is controversial. The reported prevalence of flatfoot varies and ranges from approximately 0.6%–77.9% [6]. One study reported prevalence of 19.0% [7] and another reported a prevalence of 23% including asymptomatic flatfoot [8]. The marked variation in prevalence rates may be related to ethnic or behavioral differences among study populations and different diagnostic criteria.

Diagnosis of flatfoot can be made by physical examination, radiographic assessment, and footprint analysis. Correlations between these diagnostic tools have been described [91011121314151617]. Despite the numerous studies concerning the clinical relevance of the different diagnostic tools, no study has addressed patients' self-awareness of their feet or the correlation of the self-perception with objective clinical findings.

This study prospectively collected data of participants' self-awareness about their foot shape, as well as radiographic findings and podoscopic findings. The aim was to clarify how people perceive their foot conditions and evaluate whether there are correlations with clinical findings.

A total of 1,277 individuals participated in this study. They comprised 500 males and 777 females. The mean age was 44.0 years. Of the 1,277 individuals, 488 individuals showing discordance in radiographic or podoscopic findings were excluded. The remaining 789 participants comprised 320 males and 469 females, with a mean age of 43.90 years. Of the 789, 712 (90.24%) perceived their feet as normal, 69 (8.75%) regarded their feet as flat, and 8 (1.01%) perceived their feet as cavus. According to the talometatarsal angle, 467 (59.19%) were diagnosed as normal, 174 (22.05%) as flatfeet, and 148 (18.76%) as cavus feet. Podoscope examination diagnosed 430 (54.50%) as normal, 54 (6.84%) as flatfeet, and 305 (38.66%) as cavus feet. General characteristics of the participants are provided in Table 1.

Differences between participants' self-awareness about their feet and the clinical diagnosis based on talometatarsal angle measurements were compared (Table 2). Of the 69 participants who thought their feet were flat, 41 (59.42%) were actually diagnosed as flatfeet, and 19 (27.54%) were normal according to radiographic findings. Of the 174 participants diagnosed as flatfeet by radiologic findings, only 41 (23.56%) thought their feet were flat, with 132 (75.86%) perceiving their feet to be normal. Of the 8 participants who thought their feet were cavus, 2 (25.00%) were actually diagnosed as cavus feet and 5 (62.50%) showed normal talometatarsal angles. Of the 148 participants diagnosed as cavus feet according to their talometatarsal angle, 137 (92.57%) perceived their feet as normal and only 2 (1.35%) regarded their feet as caval. The two findings were significantly different (Pearson chi-square test, p=0.000), with only slight agreement (kappa measure of agreement=0.136, p=0.000).

We also compared self-awareness with diagnosis according to the podoscopic findings (Table 3). Of the 69 individuals who answered that they had flatfeet, only 27 (39.13%) were actually diagnosed as flatfeet, with 35 (50.72%) having normal feet. Fifty-four participants were diagnosed as flatfeet according to podoscopy results; 27 (50.00%) perceived their feet as normal and the other 27 (50.00%) thought they had flatfeet. Of the 8 participants who regarded their feet as caval, 5 (62.50%) actually had cavus feet and 3 (37.50%) were normal on podoscopy. Of the 305 participants with cavus feet on podoscopy, only 5 (1.65%) thought their feet were cavus feet. The overwhelming majority (n=293, 96.07%) thought their feet were normal. These results showed a significant difference (Pearson chi-square test, p=0.000), with only slight agreement (kappa measure of agreement=0.072, p=0.000).

The mean talometatarsal angle of participants who perceived their feet as being flatfeet was −4.77°±8.04°. Those actually diagnosed as flatfeet according to podoscopy showed a mean talometatarsal angle of −8.50°±7.40° (Table 4).

Fig. 3 shows the distribution of the number of individuals who either thought they had flatfeet or who presented test findings consistent with flatfeet. It is obvious that there were more people with inconsistent findings than consistent results.

Flatfoot is a common disorder, and is likely the most recognized foot deformity in the general Korean populations. Most healthy Korean males in their 20s are mandatorily recruited for military service. Military training consists of vigorous weight-bearing physical activities including marching and mountain climbing. This physical burden likely heightens the vulnerability of soldiers to musculoskeletal pain or injuries, especially in the lower extremities. In one study, of 287 soldiers treated at a military hospital, 74.9% involved lower extremity injuries [22]. Since flatfoot may increase the risk of lower extremity injuries and pain, the Korean military qualification examination includes plantar arch assessment.

The widespread recognition of flatfoot made us wonder how Koreans perceive their plantar arches. Many studies have addressed the relationships among physical examination findings, radiographic parameters, and podoscopic findings. But, no study has addressed self-awareness. Among the various radiographic examination tools, we chose the talometatarsal angle for the present study. Previous studies concluded that the lateral talometatarsal angle is the best radiographic angle to quantify the height of the medial longitudinal arch [141923]. As a podoscopic assessment, we used Staheli arch index, which correlates with the radiographic parameters and is simple to use [202124].

There was significant disagreement between patients' perception of their own feet and actual test results. Several explanations can be offered. One possibility is that current diagnostic examinations may be insufficient for diagnosis of flatfoot. These examinations may not accurately demonstrate patients' actual symptoms and thus show poor correlations. However, considering previous demonstrated correlations between clinical symptoms and these diagnostic tools [141519], this explanation needs further study.

Another possibility is that the Korean general population may have an incorrect understanding about the concept of flatfoot. While flatfoot is a widely recognized term, it may be that few Koreans actually fully understand the pathophysiology and clinical presentations of the disorder. Especially, people are likely to think they have some pathological conditions when they actually have discomfort. This may lead people with asymptomatic flatfeet to think their feet are normal. On the other hand, there may be various clinical conditions causing foot symptoms. It could be easy for people with any foot symptoms to regard themselves as having flatfeet, as the disorder is so familiar to them while other disorders are not as familiar.

Either way, these results imply that many people may have wrong assumptions about their own foot conditions and may not properly manage their feet. Therefore it would be ideal to introduce to the population the exact definition, physiology and clinical symptoms of the flatfoot and other disorders that may cause foot symptoms as well. It would be helpful if there are ways to popularize such information via various media. An opportunity is during visits to foot clinics. This would also allow proper foot management before hasty assumptions are made. A good first step would be the dissemination of accurate information to clients by foot clinicians.