MRI-Based Morphologic Patterns of the Peroneus Quartus in a Korean Clinical Cohort: An Anatomical Study with an Illustrative Surgical Case

Background/Objectives: The peroneus quartus (PQ) is an accessory musculotendinous structure of the lateral leg with variable origin and distal attachment. Although its anatomy has been described in cadaveric and imaging studies, the morphologic patterns encountered on routine ankle MRI remain clinically relevant. This study aimed to characterize MRI-visible PQ morphology in a Korean clinical cohort and to compare the observed patterns with previously reported anatomical variants. An illustrative surgically treated case was also reviewed.

Methods

Three hundred ankle MRI examinations obtained between February 2020 and February 2024 were reviewed. After exclusion of 33 examinations in which the peroneal compartment could not be reliably assessed, 267 unique patients were included. Two readers independently evaluated PQ presence and distal attachment using predefined MRI criteria. Interobserver agreement was assessed with Cohen’s kappa. The surgically treated case was reviewed separately as an illustrative clinical correlation.