Compartment syndromes are caused by a significant increase in the tissue pressure within a closed space resulting in reduced circulation to muscles and nerves. As the tissue pressure increases, the perfusion gradient decreases and muscle and nerve ischemia occurs. Working with dogs, Heckman found irreversible muscle infarction when the tissue pressure was within 10 mm Hg of the diastolic pressure. Bernot noted that muscle subjected to ischemia before an increase in compartment pressure developed hypoxic metabolic changes when the perfusion pressure was within 40 mm Hg of the mean arterial pressure. Cellular anoxia is the final common denominator of all compartment syndromes, with myoglobin released from the injured muscle cells. Patients who have compartment syndromes may experience myoglobinuria, metabolic acidosis, and hyperkalemia, which may result in renal failure, shock, hypothermia, and cardiac arrhythmias or failure.

The most common cause of compartment syndromes is a fracture. However, virtually any condition that causes marked muscle or compartment swelling may cause a compartment syndrome, including bleeding from coagulopathies or anticoagulation; crush injuries; prolonged dependency (intravenous drug abusers, alcoholics, and stroke victims); tight casts or dressings; osteotomies; burns; reperfusion; prolonged operating room position; and military antishock trousers.

Pain out of proportion to injury is the hallmark finding in patients with a compartment syndrome. Patients note a severe, unrelenting
discomfort, which is often not relieved by narcotics. Patients may explain their pain by stating that it is intolerable, or they may lay quietly with their eyes closed in an attempt to tolerate the pain. Escalating doses of narcotics are often necessary to control the pain. There is a significant risk that clinicians may prescribe sufficient narcotics to mask the compartment syndrome, leading to a significant delay in diagnosis. Patients may also describe neurologic symptoms such as paresthesias and a loss of motor function.

Pain with passive stretch of the muscles traversing the compartment, tenseness, pain on palpation of the involved compartment, and loss of motor or sensory function are the important physical examination findings. Unfortunately, tenseness and pain on palpation are not specific for compartment syndrome and are often present in patients with fractures. Patients with a compartment syndrome in the leg exhibit severe discomfort when the toes are flexed or extended; they often do not allow the examiner to repeat the test. Many patients with compartment syndrome are not able to actively flex and extend their toes.