Illustration of pressure sore stages. A pressure sore (bedsore) is an ulcerated area of skin caused by irritation and continuous pressure on a part of the body, usually in a bedridden patient. Pressure sores are categorised in four stages. At stage 1, the pressure only affects the upper layer of the skin. The sore may feel painful, stiffer or warmer in comparison to surrounding tissue. At stage 2, the sore extends into, but not through, skin layers and the skin is broken. At stage 3, the pressure sore is a deep wound that reaches the deeper layers of the skin. At stage 4, the pressure sore is a very deep wound that may reach the muscle and bone.