Pressure ulcers arise due to a combination of situations and factors.
On a cellular level, ischemia occurs to tissue when too much pressure is applied to one area for a prolonged period of time. This pressure is usually from a bony prominence on one side and a hard surface on the other side. The soft tissue between these two surfaces is subjected to abnormal pressure. The ischemia produced leads to tissue necrosis. The tissue closest to the bone is typically the first tissue to undergo necrosis.