Background: Traumatic posterior dislocation of the sternoclavicular joint is an uncommon injury and easily missed at the acute presentation. However, all posterior sternoclavicular joint dislocations require treatment due to the life-threatening risk of injury to surrounding structures.
Case Report: A 14-year-boy presented to casualty with an acutely painful right shoulder following a fall sustained whilst playing rugby. Plain radiographs revealed no obvious abnormality and the patient was subsequently referred to the fracture clinic. Upon review by an experienced clinician, a posterior dislocation of the sternoclavicular joint was diagnosed. A CT scan confirmed the diagnosis and demonstrated no evidence of mediastinal compression. The patient proceeded to surgery for an open reduction.
Conclusions: Posterior sternoclavicular joint dislocation is an easily missed injury. The emergency physician must maintain a high index of clinical suspicion and awareness of the role of CT to aid the diagnosis of this life-threatening condition.

Keywords: posterior dislocation, Sternoclavicular Joint, computed tomography