# Congenital Absence of the Navicular Bone: A Rare Cause of Adult-Acquired Flatfoot and Posterior Tibial Tendon Dysfunction

## TL;DR

A rare case of adult flatfoot caused by a missing navicular bone highlights the importance of proper diagnosis and treatment.

## Contribution

This case report highlights congenital navicular absence as a rare cause of adult-acquired flatfoot and PTTD.

## Key findings

- Congenital absence of the navicular bone can lead to midfoot instability and flatfoot deformity.
- Navicular anomalies can exacerbate posterior tibial tendon dysfunction in adults.
- Advanced imaging is essential for diagnosing navicular-related foot conditions.

## Abstract

The navicular bone is critical for foot biomechanics, stabilizing the midfoot through its articulation with the talus and cuneiform bones. Variations, including accessory ossicles, hypoplasia, and complete absence, can lead to altered foot function. We present the case of a 58-year-old female patient who experienced persistent left foot pain. Imaging revealed the congenital absence of the navicular bone, resulting in altered biomechanics, midfoot instability, flatfoot deformity, and secondary degenerative changes. Posterior tibial tendon dysfunction (PTTD), a leading cause of adult-acquired flatfoot, is exacerbated by navicular anomalies. Advanced imaging plays a critical role in diagnosis, with treatment ranging from conservative management to surgery, depending on severity.