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 skin overlying the sacrum, coccyx, heels or hips, but other sites such as the elbows, knees, ankles or the back of the cranium can be affected. Pressure Ulcers occur due to pressure applied to soft tissue resulting in completely or partially obstructed blood flow to the soft tissues resulting in completely or partially obstructed blood flow to the soft tissue. Pressure ulcers most commonly develop in persons who are not moving about or are confined to wheelchairs. Also known as decubitus ulcers or bedsores.