This is the contraction of the toe at the mid toe joint. The toe becomes rigid and it can occur on any toe except the big toe. This condition may cause the tightening of the ligaments on the underside of the toes due to muscle problems, and is associated with arthritis.
The pronounced downward bending of the toe can cause pressure and pain. Rubbing against footwear on the top and end of the curled toe can lead to the development of corns and callus.