How do I know if I have compartment syndrome?

Compartment syndrome. The hallmark signs of acute/early compartment syndrome are: -pain out of proportion to the injury -firmness of the muscle compartment -pain with squeezing of the compartment -pain with passive stretch of the muscles in the compartment -decreased sensation this is a surgical emergency and without emergent decompression can cause loss of limb function.
See a doctor. There is an invasive procedure to measure the pressures within the compartment with a catheter. See a vascular or orthopedic surgeon. Vascular abnormaliites can be a source of symptoms of compartment syndrome especially in runners.