Bioelectric Signaling and Tendon Repair: From Endogenous Injury Currents to Percutaneous Direct-Current Stimulation—A Narrative Review

Endogenous direct-current (DC) electric fields are among the earliest signals generated after tissue injury and act as a directional cue for repair. Fields of physiological magnitude (∼40–200 mV/mm) guide cell migration (galvanotaxis), and disrupting them impairs healing while restoring them can accelerate it. Translation to tendon has lagged behind skin and bone. A conceptual fault line divides the clinical field: needle-based electrolysis therapies act by high-intensity electrolytic ablation that provokes a controlled inflammatory repair, whereas percutaneous bioelectric current stimulation (PBCS) delivers sub-milliampere DC (<500 µA) intended to act at the signaling, not the tissue-destruction, level. We review the biophysics of injury currents, the galvanotaxis of fibroblasts and tenocytes, preclinical DC effects on tendon healing, and the neurovascular pathobiology of tendinopathy, and argue that PBCS protocols should be tailored to the neurovascular ingrowth and disorganized collagen that characterize tendinopathy, instead of copying protocols developed for tissue-destroying (ablative) therapies.