Calluses

A callus may spread across the ball of your foot. This type of callus is usually due to a problem with a metatarsal (the long bone at the base of the toe, near the ball of the foot). A pinch callus may grow along the outer edge of the heel or the big toe.

Some calluses press up into the foot instead of spreading on the outside. A callus may form a central core or plug of tissue where pressure is greatest.