They are generally most common at anatomical sites over a bony prominence. In adults, the most common locations are the sacrum and the heel. This is due to the thin layer of subcutaneous tissue between the skin and bone providing minimal protection from the combined forces of pressure, shear and friction. There is often a reduced blood supply to the extremities due to co-morbidities that compromise the vascular system. These sites account for about half of all Pressure ulcers/injuries. Other sites commonly affected include the ischium, ankle, elbow, and hip. In children and neonates, the skin over the occiput is most affected. Norton et al 2018, EUPAP 2019