Influence of Pes Planus on Ankle Joint Mobility

Introduction

Ankle joint mobility contributes to injuries of lower extremities in individuals with proprioceptive problems which are related to joint stiffness.¹ Flat foot is a condition in which there is a collapse or absence of medial longitudinal arch. Calcaneal eversion is present. The center of gravity is altered, which causes stress on joint structures like spine, hip, knee and ankle, causing postural defects in all age group.² It also results in loss of shock absorbing function making the foot more prone to trauma and osteoarthritis. Loss of concavity of the sole leads to compression of nerves and vessels of the sole.^3,4 Functional activity and integrity of the ankle may be affected due to a variety of etiological factors. The ankle stiffness results in altered mechanical behavior of the ankle muscles contributing to risk of falls and impaired standing balance in daily activities. Demographic factors like body weight and height (BMI) must be considered. Navicular drop test (NDT) and Feiss line analysis can be used to determine flat foot.^1,5,6

The purpose of this comparative study was to assess the ankle mobility in individuals with and without flat foot. Any altered function and structure of the medial longitudinal arch (MLA) of the foot has been proposed as a risk factor for developing injuries due to altered biomechanics and arthrokinematics in ankle complex. Therefore, there is a need to identify the relationship between the ankle mobility and flat feet.

Material and Methods

This observational study was conducted by recruiting young adults from an institute in Mysore during April 2022. A sample size of eighty-two (N=82) was estimated using G* power 3.0.10 software with input parameters of effect size 0.3 and α =0.05. Approval for the study was obtained from the Institutional Research Committee (IRC) (Reference no: JSSMC/ IEC/05012022/05NCT/22021-22, dated 14th January 2022). A pilot study was conducted involving ten participants, the results obtained were analysed and the procedure was standardized accordingly.

All the participants were screened for inclusion and the objectives of the study were explained to the participants. Informed consent was obtained from the participants prior to the commencement of the study. The participants were selected based on the inclusion and exclusion criteria. Participants were educated on pes planus and the importance of early detection. Demographic data for each participant was collected prior to the commencement of the study as the baseline data.

Participants were taken to the study area. The screening was done using the NDT on the dominant side. The subjects in the age group of 18-24 years were selected for screening. The individual was asked to sit in the chair with their ankle on the supporting surface (step or floor) in a neutral position. The height of the chair was adjusted according to the length of the limb to keep it neutral. Individuals were asked to remove socks or foot wear if present. The whole foot was exposed. The skin over the medial aspect of the foot was cleaned prior to marking. The most prominent part of the navicular tuberosity in the medial aspect of the foot was marked by palpating with the fingers of the hand using skin markers. Then the marking was made on the paper at the level of the navicular tuberosity. The individual was asked to stand so that full weight bearing through the lower extremity was achieved, making sure that the foot is in the subtalar joint in a neutral position. Then again, the previously marked paper card was taken, and the same markings were done with reference to the point marked in the navicular tuberosity. The amount of excursion of the navicular tuberosity was measured on the paper using a ruler. A universal ruler had to be used for the entire study. An excursion of more than 9 mm was considered to be flat-footed. Normal people had an excursion of 5-9 mm.⁷

Prior to measuring range of motion, the HALO digital goniometer (HG) (Figure 1) (Model number: FGS.HMD. Gonimeter-3) was charged. To commence dorsiflexion (DF) and plantar flexion (PF), the subject was instructed to lie down in a supine position. The hip complex and the leg were enhanced in perfect alignment. While maintaining full extension of the knee, the investigator placed the participant's foot in DF, making sure the participant's foot was not in supination, pronation, external, or internal rotation. The final range of motion (ROM) was decided when the professional detected the first signs of resistance. Positioning for HALO was as follows: Using the short side of the kinesics base, the HALO digital goniometer was on the table (Hint: the HALO buttons should be on the left side of the table).⁸

For measuring the inversion and eversion, the individual was asked to short sit on the couch, hanging their legs down. The HG was placed in the medial aspect of the foot so that the laser intersected the fifth metatarsal head and calcaneum. The investigator placed the foot in inversion and eversion and recorded the data in a similar manner as dorsiflexion. All statistical tests were performed using SPSS software. Mean and standard deviation were analysed and correlation was done by Pearson correlation. P value was considered as ≤ 0.05.

Results

A total of eighty-two (N=82) participants were recruited for the study. Four participants were not included in the analysis as they were not able to complete any one of the outcome measurements. Seventy-eight participants (N=78) were included in the study, of which thirty-six (N=36) were women and forty-two (N=42) were men, with a mean age of 21.01 years (SD 1.47).

The dominant side of the subject’s mobility of dominant foot was assessed using HG which is reported in degrees. The descriptive statistics of the mobility of ankle joint and the NDT results are described in Table 1. The Pearson correlation coefficient was computed to assess the relationship between NDT and ankle RoM. There was a weak negative correlation between NDT and DF of r (76)= -.23, P=.04 and eversion of r(76)= -.19, P=.09. There was a weak positive correlation between NDT and PF of r (76)= .14, P=.21 and inversion of r (76)= .10, P=.38 (Table 2).

Discussion

In the present study, no relation between PF, inversion and eversion of ankle joints was observed. As per the findings of other studies, pes planus and the ankle's RoM are connected.¹ A relationship was found between the NDT and decreased DF in subjects with flat foot. The decreased DF resulted from increased tightness in triceps surae which resulted in excessive pronation of the foot and involvement of mid tarsal joint. Further studies must be conducted involving children aged 6-12 years to determine the influence of pes planus. Dynamic analysis of ROM must be done to understand the exact effect of flat foot during mobility.

Conclusion

The present study showed a negative correlation between ankle’s range of motion and extent of pes planus. The DF was reduced in individuals with flat foot and this may have an impact on their mobility, gait, all which can lead to injuries.

Declarations

Ethics approval and consent to participate

The project “Influence of pes planus on ankle joint mobility” has been cleared and approved by the Institutional Ethical Committee of JSS Medical College, JSSAHER, formerly and JSS University, with reference no JSSMC/IEC/05012022/05NCT/22021-22

Competing interests

The author declare that they have no competing Interests.

Funding & Acknowledgements

This study is a part of the main study funded by Rajiv Gandhi University of Health Sciences, Bangalore, India under project code UG21PHY348.

Conflict of interest

None