Compartment syndrome is a painful condition that develops when swelling takes place within an enclosed area (compartment), in which muscles, nerves, blood vessels, and bones in the compartment have no room to expand. Pressure on arteries, veins, and nerves causes extreme pain, slows circulation to the muscles and nerves, and may cause permanent damage to these tissues.

The swelling that causes compartment syndrome may be caused by decreased blood flow, trauma, bleeding, fluid buildup, or other things. Compartment syndrome is a medical emergency. It requires immediate treatment to prevent tissue death and permanent dysfunction.

Occasionally, people involved in a greatly increased level of physical activity—such as long-distance runners or new military recruits—may develop chronic compartment syndrome. With chronic compartment syndrome, symptoms are less sudden, less severe, and often improve with rest.