The toes provide a major function in creating stability of the foot during walking. The primary movement of the toes is flexion or bending down and extensor or bending up during the walking cycle. A hammertoe is a contracture of the joint in the middle of the toe most commonly seen in the second through fifth toes. It is caused by an imbalance of the flexors muscles and extensor muscles of the foot and lower leg. The flexor muscles act to bend the toes to the ground and the extensor muscles lift the toes off of the ground.
The most common cause of the flexor to extensor imbalance can be seen in the pronated foot. Excessive foot pronation can causes excessive lengthening of the foot which bends the toe by placing more pull on the flexor tendons as they attach to the toes. The pronated foot also, leads to instability of the foot which can cause the flexor muscles to pull harder in the attempt at stabilizing foot during walking. Excessively tight calf muscles can cause the extensor muscles to work harder to lift the foot off of the ground during walking which can also contribute to the bending of the toes during walking.

Pain from a hammertoe is generally due to the development of a callus or corn that occurs as a result of friction between the top of the bent toe and the surface of the shoe. Pain at the tip of the toe is caused by the excessive bend of the toe pushing into the sole of the shoe.
Treatments including callus reduction, padding to decrease friction as well as surgical options are common. Thoughtful shoe selection, including the use of wider toe box shoes as well as shoes with a deeper toe box can be integral in reducing the friction that causes the painful callus.