This review summarises the present knowledge of acute compartment syndrome, which is a time-critical diagnosis threatening both life and limb of the affected patients. Acute compartment syndrome is a clinical diagnosis, which in equivocal cases can be supported by direct intra-compartmental pressure measurement and laboratory values. Imaging can detect fractures; and non-invasive monitoring is under investigation but has not yet found clinical use. The treatment is a surgical fasciotomy, and this should be performed acutely. If diagnosis is made more than 24-48 hours after onset of symptoms, non-operative treatment should be considered.