Aims. The Chopart joint complex is a joint between the midfoot and hindfoot. The static and dynamic support system of the joint is critical for maintaining the medial longitudinal arch of the foot. Any dysfunction leads to progressive collapsing flatfoot deformity (PCFD). Often, the tibialis posterior is the primary cause; however, contrary views have also been expressed. The present investigation intends to explore the comprehensive anatomy of the support system of the Chopart joint complex to gain insight into the cause of PCFD. Methods. The study was conducted on 40 adult embalmed cadaveric lower limbs. Chopart joint complexes were dissected, and the structures supporting the joint inferiorly were observed and noted. Results. The articulating bones exhibit features like a cuboid shelf and navicular beak, which appear to offer inferior support to the joint. The expanse of the spring ligament complex is more medial than inferior, while the superomedial part is more extensive than the intermediate and inferoplantar parts. The spring ligament is reinforced by the tendons in the superomedial part (the main tendon of tibialis posterior), the inferomedial part (the plantar slip of tibialis posterior), and the master knot of Henry positioned just inferior to the gap between the inferomedial and inferoplantar bundles. Conclusion. This study highlights that the medial aspect of the talonavicular articulation has more extensive reinforcement in the form of superomedial part of spring ligament and tibialis posterior tendon. The findings are expected to prompt further research in weightbearing settings on the pathogenesis of flatfoot. Cite this article: Bone Jt Open 2024;5(4):335–342

Introduction: A.K. Henry described the region of the cross-connection between FHL tendon and FDL tendon in the mid-foot. It had been termed “master knot”. Up to now its description was not done exactly.

Aim: In this study we were investigating the exact structure of the tendons connection and possibilities of the tendons transfer in the region of foot; especially for repairing extended or neglected Achilles ruptures.

Methods: Both feet in 30 cadavers (17 men, 13 women) had been prepared. The distance from proximal part of the knot to the distal insertion of FHL and the distance from the end of FHL origin to the proximal part of the knot had been measured. This values had been compared with the foot length.

Results: In the investigated group of cadavers had not been found any direct junction between FHL and FDL tendons proximally from the branching FDL for fingers. There is an interconnection from the FHL tendon to distal part of FDL for 2nd eventually for 3rd finger (distally from FDL branching). We did not find any connection described in anatomical study of E. O’Sullivan (Clinical Anatomy18: 121 – 125, 2005).

The average distance from the point of interconnection on the FHL to its insertion was 13,8 cm (9,8 cm–19,4 cm), from the end of muscle origin 17,9 cm (15,7 cm–19,6 cm).

The approximate distances after the conversion to the foot length were 0,70 times foot length and 0,55 times foot length.

Conclusions: There is no direct junction between FHL and FDL tendons proximally from the branching FDL for fingers. The suture of the tendons distally from the cut of transferred tendon and proximally from FDL branching is necessary to keep the correct flexion of all fingers.