Depicts pressure sore (bedsore, or decubitus ulcer) formation. Shows common sites over bony prominences such as the back of the head, shoulder, sacrum and heel bone. A histological reveals formation due to compression between a bony prominence and soft tissues. Progress of ulcer: Stage 1 where only a reddish area appears on the skin to Stage 4 where necrosis (tissue death) penetrates through the skin, fat, fascia, subcutaneous tissues, muscle and bone.