Retrosternal displacement of the medial clavicular metaphysis after a medial physeal fracture is a rare and potentially fatal injury because of possible damage of neurovascular structures, trachea and oesophagus. As the medial clavicular epiphysis does not ossify until 18-20 years of age and the medial clavicular physis is the last to close, around 22-25 years of age, this injury is difficult to demonstrate with plain radiographs in younger patients and is often mistaken for a sternoclavicular joint dislocation. We report on a 16-year-old boy with a fracture of the medial clavicular physis with retrosternal displacement of the metaphysis that was diagnosed with MRI, and discuss the diagnostic tools and treatment options in this rare injury.