History of pain post exercise and elevated CK leads to a diagnosis of rhabdomyolysis. One of the complications of this condition is compartment syndrome. The clinical finding of anterior compartment syndrome is presumably secondary to the muscular swelling.  If the intramuscular signal change was secondary to compartment syndrome, none of the anterior compartment musculature would have been spared.

Rhabdomyolysis can be due to a number of conditions including:  excessive exercise, crush injury, arterial occlusion, metabolic disturbance, drugs and toxins, infection, inflammation and congenital disorders. Excessive exercise and heat stroke are probably the most common cause of severe rhabdomyolysis.

MRI is usually not required for the diagnosis of rhabdomyolysis since it is a clinical diagnosis. It may be used for staging or follow-up or as in this case to confirm absence of another condition such as vascular malformation and hemorrhage that may have led to the muscle swelling.