Brachymetatarsia is a condition in which one of the bones in the front of the foot is significantly shorter than the others. Although it may affect any of the five metatarsals, it most commonly affects the fourth metatarsal. Looking at the foot, it might appear that the fourth toe itself is shorter than the adjacent toes. Sometimes it may even appear as if the fourth toe is raised up, with the third and fifth toes touching each other below it. 
 
The condition occurs when the affected metatarsal bone fails to develop fully, or its growth plate closes prematurely. It is easily diagnosed with an x-ray.

Beyond concerns about the toe’s appearance, the shortened metatarsal may not contact the ground properly or carry its share of the person's body weight, resulting in pain and discomfort. It may also change the appearance and contour of the ball of the foot, making shoe selection difficult.
 
In some cases brachymetatarsia causes no pain or discomfort, and may be treated with careful shoe selection. In others, surgical treatment may be required.