A compartment syndrome is a condition in which increased pressure a confined fascial space causes decreased capillary blood flow and tissue function below a level necessary for viability. There are a variety of possible etiologies, such as increased compartment content (hematoma, edema, exertion, intoxication) and decreased compartment size (constrictive dressings and casts, closure of fascial defects). The pathophysiology of compartment syndrome is based on the arteriovenous gradient theory. The high pressure within the compartment leads to a decrease in the arteriovenous gradient, to a lowering of tissue PO2 and finally to a metabolic deficit. The tolerance of increased pressure by nerve and muscle is defined by the relationship of mean arterial pressure to tissue pressure and not by absolute tissue pressure.