There are many types of bed sores. These ulcers can occur anywhere on the body, including the head, shoulder blades, elbows, hips, knees and heels. Ulcers most difficult to treat are often located at or near the sacrum (right above the tail bone). Offloading weight (and the resulting pressure) from a bed sore is the most important step toward healing. Unlike ulcers at other locations, the human hip is difficult to offload for long periods. For example, heel ulcers occur frequently, but they have been treated for centuries with pillows under the calf. In Africa, nurses often use, with much success, inflated latex gloves taped under calves to treat heel ulcers. In the US, most heel ulcer patients are fitted with inexpensive "booties" to offload the heels, regardless of the type of mattress they are using.
A support surface's pressures relieving performances are critical when used under a person's bottom. Due to human physiology, aside from turning a person onto his/her side, there is no simple way of offloading the weight off of a person bottom. The problem is magnified by the many bed bound people who are incontinent (waste products near open wounds), and the most who spend their time with their beds at an incline (can't bend a body sideways) to sleep, read, watch TV or eat. Since the human body is mostly supported by the hip region when the bed is at an incline, the pressures on a person's bottom are much greater than when he/she is lying flat at a supine position. The most effective support surfaces to prevent or treat bed sores will have been tested at inclines to produce the lowest pressures.