BACKGROUND: Peroneal tendon injuries, particularly of the peroneus longus, contribute to lateral ankle pain and instability. However, limited literature addresses the anatomical influence of the cuboid tunnel and the os peroneum on such injuries. This study investigates histological changes in the peroneus longus tendon and their relationship to cuboid tunnel dimensions, os peroneum presence, and age. METHODS: This cross-sectional study examined 60 peroneus longus tendons from 30 cadavers (ages 15-71). Tendons were sectioned and histologically analyzed for cellularity and collagen composition. Cuboid tunnel dimensions were measured, and the presence of os peroneum, an accessory ossicle located within the peroneus longus tendon, was recorded. Statistical correlations were performed. RESULTS: Increased type III collagen and cellularity were significantly associated with advanced age, reduced tunnel width, and increased tunnel height (p <
0.05). No significant association was found with tunnel length or os peroneum presence. CONCLUSIONS: Age, reduced cuboid tunnel width, and increased tunnel height are associated with peroneus longus tendon degeneration, with collagen type I replacement by type III, predisposing factors for tendinosis. LEVEL OF EVIDENCE: Level IV (Anatomical Study).