At this stage, there may be undermining and/or tunneling that makes the wound much larger than it may seem on the surface. Stage 3 involves the full thickness of the skin and may extend into the subcutaneous tissue layer granulation tissue and epibole (rolled wound edges) are often present. Stages 3 and 4 pressure ulcers have deeper involvement of underlying tissue with more extensive destruction. Symptoms of Stage 3 and Stage 4 Pressure Ulcers Stage 4 pressure ulcers extend even deeper, exposing underlying muscle, tendon, cartilage or bone. Stage 3 pressure ulcers involve full-thickness skin loss potentially extending into the subcutaneous tissue layer. Pressure ulcers are localized areas of tissue necrosis that typically develop when soft tissue is compressed between a bony prominence and an external surface for a long period of time.