Off-weighting of the foot is a term that means pressure reduction. Persons with diabetes and feeling loss in the feet or neuropathy are prone to increased weight bearing pressures on the soles of the feet. Increased pressures can lead to foot ulcers or sores and prevent sores from healing. Off-weighting of the foot is used to treat ulcers as well as to prevent ulcers.

The fingertip and pane of glass analogy, discussed in the “Causes” of foot ulcers section, is a good way to explain the effect of increased pressure on the foot. In other words, the increased pressure against the foot cuts off the blood supply and can result in foot ulcers as well as prevent ulcers from healing. Persons with diabetes and neuropathy are especially susceptible to the development of ulcers because they cannot feel the increased pressure and associated pain. In a person with good feeling in the feet, the increased pressure causes pain. This pain response is a form of protection. The pain alerts the person to the fact that something is causing harm or injury.

Prominent bones on the feet such as dropped metatarsals, hammertoes or bunions are particularly prone to increased pressure from walking and/or wearing shoes. Persons with diabetes, neuropathy, and deformity are at increased risk for the development of pressure sores. In these situations off weighting is necessary to try and prevent sores. There are many different ways to off-weight a foot. It may be as simple as properly fitted shoes with cushioned insoles or it may be more involved and require a cast or healing sandal.

Improper off-weighting can cause problems. For instance complete pressure reduction over one area on the foot means that the extra pressure has to be taken up by another part of the foot. This can lead to overload and new pressure related problems. If there was a sore under the big toe and a cutout pad was placed under the big toe to keep all pressure off the toe then the four smaller toes would suddenly have to take up more pressure. To put it another way the four smaller toes would have to carry the amount of weight meant for all five toes. The big toe may heal but at the same time new sore(s) may form over the smaller toes. Therefore, when selecting a means of off weighting it is important to redistribute the pressure evenly so that one are is not off weighted at the expense of another area.

There are lots of different types of off-weighting devices including casts and shoes/ insoles/ inserts / orthotics. For a device to be effective it must distribute the weight evenly. Total contact is the term used to describe even weight distribution. Appropriate off- weighting is thus pressure reduction over one part of the foot by evenly redistributing that pressure over the entire foot. Without equal pressure redistribution new sores may develop on other areas of the foot.

Timothy P. Kalla, BSc, DPM, FACFAS