Background: Flatfoot, also known as fallen arches, is a common foot condition characterized by a lack of arch support and abnormal pronation. It can be classified into two types: Flexible Flatfoot and Rigid Flatfoot. FFT is the most common form, accounting for approximately 70% of cases, while RFT is less common but more severe. Obesity is a major risk factor for flatfoot deformity, as excess weight puts additional stress on the foot. Weakness of the Tibialis Posterior Tendon, a key stabilizer of the arch, is also a significant contributor to flatfoot development.

Objectives:  To determine the prevalence of Flexible Flatfoot (FFT) and Rigid Flatfoot (RFT) in obese individuals and explore their association with weakness of the Tibialis Posterior Tendon (TPT).

Materials and method: This study included 377 participants aged between 18 and 40 years old, with a diverse distribution across different age groups. Both genders were included with BMI of the obese category having flatfoot. In the current study, the focus was on evaluating the prevalence of flatfoot and types of flatfoot among the obese participants, distinguishing between unilateral and bilateral occurrences. Assessments, including the Navicular drop and single-limb heel-rise tests, were conducted to gather comprehensive data on foot structure and function. Statistical analyses also included Pearson chi-square tests to explore the associations between the prevalence and types of flatfoot with weakness of the tibialis posterior tendon.

Results: The number of participants included in this study was 377 with minimum age of 18 and maximum age of 40 years. Among the participants, there were 158 men and 219 women. Out of 377 individuals, 87 (23.1%) were unilateral and 290 (76.9%) were bilateral flatfoot. There were 26 (6.9%), 34 (9%), and 221 (58.6%) unilateral right, unilateral left and bilateral flexible flatfoot respectively. And 15 (4%), 10 (2.7%), and 71 (18.8%) unilateral right, unilateral left and bilateral rigid flatfoot respectively. There were 281 (74.5%) participants who had flexible flatfoot and 96 (25.5%) had rigid flatfoot. The Pearson chi-square test revealed a statistically significant strong association (p<0.001) between flatfoot occurrence and weakness of tibialis posterior tendon.

Conclusion: This study shows that there is a significant prevalence of both FFT and RFT in obese people and flexible flatfoot is more common than rigid flatfoot and the occurrence of flatfoot is strongly associated with Tibialis Posterior Tendon weakness.

Keywords: Flexible flatfoot, Obese, Rigid flatfoot, Tibialis posterior weakness