Brachymetatarsia or hypoplastic metatarsal is a condition in which there is one or more abnormally short or overlapping toes metatarsals. This condition may result due to a congenital defect or it may be an acquired condition. It most frequently involves the fourth metatarsal. If it involves the first metatarsal, the condition is known as Morton's syndrome. Treatment is via a number of differing surgical procedures.

Congenital causes include: Aarskog syndrome, Albright's hereditary osteodystrophy, and Apert syndrome. Can be caused by a trauma, although the exact mechanism is not known.

The most common symptom experienced due to Morton's toe is callusing and/or discomfort of the ball of the foot at the base of the second toe. The first metatarsal head would normally bear the majority of a person's body weight during the propulsive phases of gait, but because the second metatarsal head is farthest forward, the force is transferred there. Pain may also be felt in the arch of the foot, at the ankleward end of the first and second metatarsals.

In shoe-wearing cultures, Morton's toe can be problematic. For instance, wearing shoes with a profile that does not accommodate a longer second toe may cause foot pain. A small (80-person) study found no statistically significant difference in the frequency of longer second toes between people with and without ingrown toenails, but tight and ill-fitting shoes are generally considered to increase the risk of ingrown toenails, and shoes are often too tight on the toes.

Morton's toe is the condition of a shortened first metatarsal in relation to the second metatarsal. It is a type of brachymetatarsia.

The metatarsal bones behind the toes vary in relative length. For most feet, a smooth curve can be traced through the joints at the bases of the toes. But in Morton's foot, the line has to bend more sharply to go through the base of the big toe, as shown in the diagram.

This is because the first metatarsal, behind the big toe, is short compared to the second metatarsal, next to it. The longer second metatarsal puts the joint at the base of the second toe (the second metatarsal-phalangeal, or MTP, joint) farther forward.

If the big toe and the second toe are the same length (as measured from the MPT joint to the tip, including only the phalanges), then the second toe will protrude farther than the big toe, as shown in the photo. If the second toe is shorter than the big toe, the big toe may still protrude the farthest, or there may be little difference, as shown in the X-ray.