Underlapping toes usually involve the fourth and fifth toes. (A special form of underlapping toes is called congenital curly toes.)
The cause of underlapping toes is generally unknown. They may be caused by an imbalance in muscle strength of the small muscles of the foot.
If deformed toes are flexible, a simple release of the tendon in the bottom of the toe will allow for them to straighten. If the deformity is rigid, surgery may be needed to remove a small portion of the bone in the toe.
Overlapping toes are characterized by one toe lying on top of an adjacent toe. The fifth toe is the most affected. Overlapping toes may develop in the unborn fetus.
Passive stretching and adhesive taping is most commonly used to correct overlapping toes in infants, but the deformity usually recurs.
Such deformities can sometimes be surgically corrected by releasing the tendon and soft tissues about the joint at the base of the fifth toe. In some extreme cases, a pin may be surgically inserted to hold the toe in a straighten position. The pin, which exits the tip of the toe, may be left in place for up to three weeks.