People who typically sleep on their side are familiar with the discomfort that can result from resting one knee on the other while sleeping. It is not only uncomfortable at the time, but can lead to further pain in the hip and lower back, because of the unnatural positioning of the knees. The knee pillow is an orthopedic pillow designed to ease pain in the back, hip, and knee areas. This is accomplished by placing the pillow between the knees at night, keeping them separate and thereby reducing strain on the hipbones.
Most knee pillows are either hourglass shaped, or have a rectangular form. A knee pillow with an hourglass shape tends to stay in place overnight fairly well, because of how it contours to the general shape of the knees and legs. Since a rectangular knee pillow does not have this advantage, some models are available which include a fabric strap, which wraps around one leg to keep the pillow in place. The strap attaches to the pillow cover, which is machine washable.
Another interesting design variation of the knee pillow is one which has an hourglass or butterfly shape on both sides, but can open up in the middle. This type actually has hinges on it to allow the pillow to open up and be placed flat on a bed. When open, this kind of knee pillow can be used for head and neck support, or for leg elevation. In this way, this kind of knee pillow can be used by a person who sleeps on his back as well as someone who sleeps on his side.
One type of specialized knee pillow is the kind made of Memory Foam™. Memory Foam™ is a material made of polyurethane, with additional chemicals that increase its density and thickness. It has the property of being able to conform to body contours exactly, because of its amorphous nature. This effect is visible, for example, when a person presses his hand into the foam and then removes it. For a short time after, the foam “remembers” the hand and maintains the impression made by it.
This type of material is well-suited to use in knee pillows. Its ability to contour exactly to a person’s body keeps the pillow in place overnight, as well as providing the correct amount of support wherever it is needed. Memory Foam™ was originally developed by the National Aeronautics and Space Administration (NASA) of the United States. It was never actually used by the space program, but has since found use in numerous orthopedic and medical applications.