Calluses are thickened portions of skin that appear on the body in areas receiving high amounts of friction or irritation. A seasoned guitar player could point to the toughened areas on her fingers from years of strumming, or a mechanic from wielding tools day after day. Most of us remember the reasons we develop calluses on our hands, but usually we can’t quite recall when or why the calluses on our feet showed up. We wear shoes more often than not, and most people aren’t playing instruments with their toes. So why do we get calluses on our feet?
Calluses on the feet are similar to those on the hands in that they appear in high pressure areas. However, since we walk on them, our feet receive a unique set of pressures. Not only do our feet pound against the ground with each step we take, they must also receive the impact of the body’s weight simultaneously. How this force from the body is distributed in the feet depends on the anatomy of the body and the way a person walks. If the foot structure is altered due to a deformity or a gait problem (such as limping or a shortened limb), it causes forces to be distributed unevenly in the feet. This uneven distribution can create areas of high pressure. Of course, this alone will not create a callus. But add in the repetitive motion of walking that puts even more stress on areas already under high pressure, and a callus eventually develops.
High pressure areas and their associated calluses can occur due to several conditions. In a foot with hallux abducto valgus (HAV), the big toe is deviated toward the outside of the body and the big toe joint becomes flexible and unstable. In this situation, excessive force is placed on the outside of the big toe and the ball of the foot beneath the second toe. This causes calluses to appear on the outside of the great toe and on the sole of the foot under the second toe. Similarly, in a person who pronates excessively, calluses appear on the ball of the foot and the side of the big toe due to more force on these areas when walking. Someone who has a hammertoe will walk with the toe bent, so more force will be placed on the small part of the toe touching the ground. This creates a callus on the bottom tip of the hammertoe, and a corn on the top of the toe where it hits the shoe.
Because of the multiple factors involved in their development, treatment of calluses involves more than just removing them. A podiatrist needs to address the underlying causes in order to prevent a painful callus from persisting.