Hammertoe is a deformity of the joints of the second, third, fourth, or fifth toe. The deformity causes the toe to bend downward at the middle joint. The condition is most commonly caused by structural or neurological changes that cause a muscle/tendon imbalance. It can be aggravated by wearing ill-fitting shoes in which the toes are tight and cramped. Hammertoe usually starts as a mild deformity but worsens over time. If left untreated, the toe will lose flexibility and become more rigid, and will not respond to non-surgical treatment.