Forefoot pes cavus is a cardinal sign of Charcot-Marie-Tooth disease (CMT). This review is focused on the pathophysiology of pes cavus in CMT1A duplication, which is the most common subtype of the disease. Assessment of foot deformities in CMT1A, their prevalence and proposed mechanisms, and recent contributions of magnetic resonance imaging studies of lower-leg and foot musculature are revised. Special attention is given to papers on foot deformities at initial stages of the disease. We conclude that pes cavus is an early and age-dependent manifestation of CMT1A duplication. Selective denervation of intrinsic foot musculature, particularly of the lumbricals, and not imbalance of lower-leg muscles, seems to be the initial mechanism causing reduced ankle flexibility and forefoot cavus deformity.