Most PrUs occur on the lower half of the body, primarily within the pelvic girdle.
Susceptible areas include the greater trochanter of the femur, ischial tuberosity, sacrum,
iliac crest, lateral malleolus, occiput, chin, elbow, scapula, and calcaneus. Sustained light
pressure or transient intense pressure can cause a PrU. Tissue damage may occur after less
than 1 hour of unrelieved pressure. PrUs may develop within 2 days of an insult/injury or
manifest later as a result of continuous soft tissue injury. PrUs can remain undetected—in
some cases for up to 7 days—after the causal injury because they can develop slowly or
develop during a period of infrequent skin assessment.