The hammer toe, claw toe, and mallet toe are all deformities of the foot and are most often contributed to wearing tight or compressive footwear. Sometimes these deformities can be congenital, or due to other problems, but the most common reason is due to footwear. Each of the lesser toes (all but the big toe) has three bones. The deformities, a hammer toe, claw toe, and mallet toe, are all due to abnormal positions of the bones at the joints between the bones and are often caused by an imbalance in the tendons attaching to these toes.
A claw toe is a toe that is contracted at the PIP and DIP joints (middle and end joints in the toe), and can lead to severe pressure and pain. Ligaments and tendons that have tightened cause the toe's joints to curl downwards. Claw toes may occur in any toe, except the big toe. There is often discomfort at the top part of the toe that is rubbing against the shoe and at the end of the toe that is pressed against the bottom of the shoe.
A hammer is a deformity of the toe, in which the end of the toe is bent downwards from the middle joint. This most often occurs in the second toe, and is often the result of a bunion (in the big toe) pushing on the second toe. A painful corn or callus often forms on the top of the first joint in the toe due to it rubbing on shoes;