The Science of Peroneal Tendinopathy

Peroneal tendinopathy affects the fibularis longus and brevis tendons that run behind your lateral malleolus (outer ankle bone). These tendons are crucial for ankle stability, particularly during walking on uneven surfaces, and help prevent ankle sprains by providing lateral stability. The peroneal tendons are subject to significant mechanical stress as they navigate around the sharp posterior edge of the fibula, held in place by the superior peroneal retinaculum. This anatomical arrangement makes them vulnerable to friction and degenerative changes, particularly when the retinaculum is damaged or when there are underlying biomechanical issues. Tendinopathy develops when the cumulative load on these tendons exceeds their adaptive capacity. This leads to a failed healing response characterized by disorganized collagen, increased ground substance, and neovascularization. The result is a painful, thickened tendon with reduced mechanical properties. The condition often develops in conjunction with chronic ankle instability, where recurrent ankle sprains lead to peroneal muscle weakness and altered biomechanics. Research shows that individuals with chronic ankle instability demonstrate reduced and delayed activation of peroneal muscles, creating a cycle where weak peroneals increase ankle instability, leading to further tendon stress and degeneration. This relationship explains why up to 70% of people with chronic ankle instability may develop secondary peroneal tendinopathy.