The smallest four toes of each foot have three bony segments connected by two joints, just as the fingers do. Hammertoe is a deformity in which one or more of the small toes develops a bend at the joint between the first and second segments so that the tip of the toe turns downward, making it looks like a hammer or claw. The second toe is affected most often.
Most hammertoes are caused by wearing ill-fitting, tight or high-heeled shoes over a long period of time. Shoes that don't fit well can crowd the toes, putting pressure on the middle toes and causing them to curl downward. The condition may be more likely when the second toe is longer than the first toe or when the arch of the foot is flat. Hammertoe can also be present at birth (congenital). Hammertoe also can be caused by a bunion, which is the knobby bump that sometimes develops at the side of the big toe. A bunion causes the big toe to bend toward the other toes. The big toe can then overlap and crowd the smaller toes. Occasionally, a hammertoe is inherited or caused by arthritis in the toe joint.
If the toes remain in the hammertoe position for long periods, the tendons on the top of the foot will tighten over time because they are not stretched to their full length. Eventually, the tendons shorten enough that the toe stays bent, even when shoes are not being worn.