BED SORES, also known as decubitus ulcers or PRESSURE ULCERS , are localized injuries to the skin and/or underlying tissue that usually occur over a bony prominence as a result of pressure, or pressure in combination with shear and/or friction. The most common sites are the sacrum, coccyx, heels or the hips, but other sites such as the elbows, knees, ankle the back of the cranium can be affected.