Diabetic muscle infarction (DMI) is a rare complication of longstanding, poorly controlled diabetes. Only a few cases have been reported in the literature. The case of a 34-year-old man with a 7-year history of type 2 diabetes mellitus, with sudden onset of left thigh pain, is described here. A final diagnosis of DMI was made, the pathophysiology of which remains unclear. MRI findings were diagnostic and characteristic. The management of this condition is usually symptomatic. Short-term prognosis is very good; however, the recurrence rate is high. Long-term prognosis is poor, with most patients dying from cardiovascular complications of diabetes within 5 years of diagnosis. This case supports the need for a high index of suspicion, when a poorly controlled patient with diabetes presents with non-traumatic limb pain.