The authors report the occurrence of an occult manubriosternal joint injury in the initial evaluation on a patient with a thoracic spine fracture (T9). This T9 fracture was diagnosed in a 37-year-old man and was associated with a partial neurological deficit. At the initial evaluation, the radiographs produced did not show the manubriosternal joint injury. During rehabilitation, after surgical stabilization of the thoracic spine fracture, the patient suddenly felt an intense pain accompanied by deformation at the sternal level. From imaging examinations, manubriosternal luxation was diagnosed. Because of recurrence of the luxation and the incapacitating pain, open reduction and fixation of the manubriosternal joint had to be performed. At the 12-month follow-up, the patient presented complete recovery of the neurological lesion, consolidation of the arthrodesis on the T7-T11 vertebral segment and maintenance of the reduction of the manubriosternal joint, which was asymptomatic during daily activities.