Imaging-based prevalence of the peroneus quartus muscle and its association with peroneal tendon pathology: a systematic review and meta-analysis.

OBJECTIVE: To determine the imaging-based prevalence of the peroneus quartus muscle and to quantify concurrent peroneal tendon pathology among individuals with this anatomical variant. MATERIALS AND METHODS: A systematic review and meta-analysis were conducted following PRISMA 2020 guidelines. PubMed, EMBASE and Cochrane were searched from inception to 2025 for imaging-based studies reporting peroneus quartus prevalence. Overall prevalence was estimated using generalized linear mixed models with random effects. Heterogeneity was assessed using the I² statistic. Risk of bias was evaluated using design-specific Joanna Briggs Institute critical appraisal checklists. Subgroup analyses examined sex and laterality distribution among positive cases. RESULTS: Seventeen studies comprising 3,725 ankle imaging examinations were included. The overall prevalence of the peroneus quartus was 11% (95% CI: 8-15%), with substantial heterogeneity (I² = 80.5%). Among six studies (315 positive ankles), peroneal tendon pathology was present in 51.4% (95% CI: 41.9-60.8%). In three studies reporting tears in ankles with and without the peroneus quartus, its presence was associated with higher odds of peroneal tendon tears (pooled odds ratio 3.40, 95% CI: 2.03-5.68; I² = 0%; p < 0.001). The majority of studies (58.8%) were classified as low risk of bias. CONCLUSION: The peroneus quartus muscle is identified in approximately one of nine ankle imaging examinations, and in studies with a comparison group its presence was associated with higher odds of peroneal tendon tears. This supports the proposed crowding-effect hypothesis, although a causal relationship remains to be established.