Heavy weight of foot
• Sharp posterior calcaneus
• Thin soft tissue padding; little to no muscle
• Blood supply via peroneal artery
• Diabetes
• Edema
• Leg spasms, agitation
• Dementia
• Muscle very sensitive to pressure & ischemia
• Poor perfusion/vasopressors
• IMMOBILITY: ≈87% of the cases; #1 PU risk factor