In the United States, the most frequent and common cause for a high arch, or cavus foot, is a form of muscular dystrophy called hereditary sensorimotor neuropathy.
Most people recognize this by the more commonly used name of Charcot Marie Tooth disease (CMT). This is a disease of the muscles and the nerves of the legs, and occasionally of the hands, in which certain muscles weaken while others retain their strength.
The condition is transmitted as an autosomal dominant condition, which means – statistically - that 50-percent of hereditary offspring inherit the disorder. Charcot Marie Tooth disease occurs in both children and adults, and once the deformity is present in a child, it typically is progressive. This means the deformity will get worse as a result of the muscle imbalance and weakness.
Although the pattern of muscle and nerve damage may be similar through the generations in a family, this is not always the case, and every cavus foot is unique.
The muscle imbalance around the foot and ankle gives rise to a typical pattern of deformity in addition to the high arch (known as cavus). The bone under the big toe (called the first metatarsal) can become very prominent and the toes can curl or clench like a fist (called claw toes). Excessive amount of weight may be placed on the ball and heel of the foot, which can lead to the ankle weakening and giving way (this is referred to as ankle instability) and soreness.
Calluses and sometimes stress fractures may occur where the foot is exposed to extra friction or pressure, such as on the outer (or lateral) border of the foot.
The deformity of the high arch foot develops because the muscles that pull the foot inward (inversion) remain strong, while those that pull the foot outward (eversion) are weak or absent. The muscle that remains very strong is called the posterior tibial muscle, and the muscle that gets weak is the peroneus brevis muscle.
Another common problem in Charcot Marie Tooth disease is the presence of a foot drop. This means that the muscle that pulls the foot (the anterior tibial muscle) upward is weak or paralyzed, leading to an abnormal dropping of the foot when walking.