Because many diabetic patients suffer neuropathy, which gives rise to a compromised sense of touch in their feet, it is not uncommon for them to be wearing improperly fitted shoes.  Because their foot is not in pain, they do not consider it to be diseased or at risk.  In fact, because a neuropathic patient may not even feel their shoe unless it is too tight, it is very common for them to present with a shoe that fits too short, narrow, or both. 

Improperly fitted shoes may increase pressures upon the superficial surfaces of the foot. Compressive pressures force skin inward against bony prominences of the foot.  This inward pressure contributes to dense patches of skin called calluses. 

When shoes are too tight, skin is held tight in place against the inside of the shoe.  Shear pressures cause bony prominences of the foot to move against the inside surfaces of the skin, again, contributing to calluses.  Because calluses are dense and do not absorb shock, continued pressure upon them ultimately results in ulceration.

Because unnoticed ulcers commonly become infected, and infected ulcers may give rise to disastrous problems, it is critical that a shoe fitting reduces compression and shear forces upon the foot.